Work Header

The Art of Drowning

Chapter Text

Denki knows full well that there’s never really been a question needed as to whether the mer exist. They ‘exist’ to humanity these days in the same way the true fae and titans do: in fossils and relics, and stories from an age when magic held the world carefully in its palms and instilled new wonders with every gentle whisper.  

It’s not like magic is gone— far from it. But the creatures that breathed magic, bled it, held together by miracles and timelessness and enigma… well, they’re another story. It’s a basic fact established by his current employers, afterall. As a marine technician aboard the expedition ship RV Shinkai Maru with the strangest collection of magizoology researchers and interns he could have imagined, he’s more in tune with the history of the mer than your average joe.

 So, yes. He knows merfolk existed , once upon a time. But after centuries of silence from beneath the waves, he—like everyone else—had accepted their disappearance alongside so many other mythical species. 

Which is why he’s having a hard time comprehending the visual feed from his sea rover.

“Erm— Uraraka?” he calls out a bit shakily, unwilling to pull his gaze from the screen in case the drifting purple-grey shape disappears. He’s having to nudge the rover every few seconds to keep the thing in the headlights; as of yet it hasn’t made any sharp moves at all, but it would be just his luck for something to happen the second he takes his eyes off it.

But there’s no response from the marine veterinarian intern; she must still be in the break room. Instead, he reaches blindly along the table towards his left, tapping and waving to get the attention of his fellow engineer, a surly blonde wearing headphones with the music so loud Denki can almost make out the words. Bakugou’s never been friendly by any means, but Denki’s desperate. He needs someone else’s eyes, anyone’s — just to offload some of his shock, if nothing else.

His hand is swatted away, followed by a grouchy “What,” that’s a bit louder than absolutely necessary. But at least he has the jerk’s attention.

“I need you to see this,” Denki says, adding a quick gesture to the screen. “I can’t— I can’t tell what I’m looking at.”

“Wouldn’t be the first time.”

“Bakugou, please. Come look. I think it’s… it’s a…” he swallows, unable to push the word past his teeth. If he says it and he’s wrong, Bakugou will be shouting the mistake through the mess hall at dinner, and Denki won’t live it down for the rest of the expedition. 

Thankfully, Bakugou saves him the potential embarrassment by grumbling and swinging his chair closer.

They peer at the shape together. The grainy rover camera isn’t the best at picking up details, and down where it’s been chugging along everything’s got a distorting blue hue in one way or another, but still— this stands out.

What had drawn Denki’s attention was a long, aubergine-colored tail and violet fin plumage that’s drifting broadly around the end and sides like sheets of silk. The rover’s glow catches a shine on some harder scales that glint like embedded amethysts in the light. But now, Denki holds his breath and maneuvers the rover once again to the view that had his heart hammering in his chest and hopes caught in his throat; the beams slide upward from the tail across a very humanoid torso.

He hears Bakugou’s low intake of breath, and for a moment the only noise apart from the far-off engines was the music still playing, weak and tinny, from the headphones around the other man’s neck. Then: “Move— move the fuck over, Creaky, let me...”

Denki ignores the nickname for once, pulling away from the controls. 

Bakugou slides into place, eyebrows knitted and hands expertly working the controls. The rover strafes to the side, pivoting around the unmoving creature. As it shifts, the beam tracks down an honest-to-gods arm that ends in five taloned digits, lax and half-curled where it rests just inches from the camera. 

Beside him, Bakugou lets out a quiet ‘what the fuck’ and that’s enough for Denki to let a thrilled grin tear across his face, because holy shit, this is real.

And then the view feed rolls on, and there’s a shoulder, then a gilled neck, and finally face with a fin-like ear on either side and closed eyes and—

“How far down’s this rover?” Bakugou asks sharply. His voice is surprisingly neutral for what’s happening, but the tension in his back and slightly wider-than-normal eyes give him away.

“Only like, two-forty.”

“Does it have its net equipped?”

“Ye—” Denki cuts himself off, finally tearing his gaze away from the merman (again, holy shit ) to stare at his coworker. “Y-yeah... it does. Are you going to…”

“I ain’t going to believe this isn’t some dumbass prank til I see it with my own eyes.” He puts his lower lip between his teeth as the rover comes back around, shuffling it backwards until the entire prone, drifting body of the creature fits within the net deployment guides on screen. “And if it ain’t a prank...” he starts slowly, then closes his mouth. In lieu of trying to find the right words to fit this unforeseeable circumstance, he turns his severe stare to Denki. “Go find the parakeet guy and bring him to the starboard docking pool.”

Denki blinks. “Parakeet guy?” 

“That one blonde researcher that’s obsessed with these fuckers. Squawks nonstop during mess. Used to have a radio show?”

Right. “Professor Yamada,” he mumbles, not that he thinks Bakugou will bother committing it to memory, if the fact that he refers to nobody by name is anything to go by. 

Bakugou grunts in acknowledgement, and then smacks the net deployment button. Denki watches with bated breath over his shoulder as ropes snap out from a space beneath the rover’s camera and snag around the creature, which… doesn’t react. That’s not promising.

Denki hauls his legs around with shaky hands, careful not to bash the mechanisms of his knee and calf braces against the edge of the desk. Really, Bakugou should be the one going to get the research team if they were gunning for speed, but he supposes this is his colleague’s way of giving Denki the credit of the find. He appreciates it— even if the dude’s an ass. 

He shoves himself to his feet, taking a moment to find his balance. On the screen, the merman has yet to move despite the slow reeling-in of the net.

“Go on, and don’t fucking fall over on the way,” Bakugou growls, shoving Denki’s cane roughly into his hands. “You better fucking have it aboard by the time I get up there if I’m putting in all the goddamn work. Go.

Denki goes.



“...I-I swear I’m not fucking with you— er— pardon my French, sir,” Denki trails on in as quiet of a voice he can, growing increasingly anxious at the stillness of Professor Yamada’s normally-exuberant face. His legs ache from pushing them so hard, and it’s taking all his admittedly limited self-control to not sit on the ledge of the docking pool. “Bakugou wouldn’t have asked me to get you if he didn’t believe it too, I think.”

It’s not only Yamada’s current state that makes him nervous. A few steps away is the professor’s husband, with tangled black hair to his shoulders and a near-permanent exhausted expression. The man has never bothered to introduce himself. Denki’s not sure the guy’s even a researcher, to be totally honest. Or even a fan of the ocean at all. He can’t recall ever seeing him anywhere other than below-decks, skulking in the shadows or tucked into an obnoxious yellow sleeping bag.

But they’re both here now, and frighteningly alert, not saying a word as the whirring machinery in the room languidly works to raise the rover and its captive. Denki shifts more weight onto his cane with a wince and a soft, sharp inhale.

The black-haired man glances over at him at that, and Denki ducks his head instinctively for interrupting his solemn contemplation. But instead of chastising him, the guy slinks over to the far wall to fetch one of the janky plastic folding chairs. 

On his return, he props it open next to Denki. “Sit,” His voice is unexpectedly smooth.

Denki nods gratefully and takes the seat. The aching falls away almost entirely and he sighs, not for the first time wishing it would stay that way. Seven years of healing and therapy could only do so much to remedy one brainless teenage error in judgment.

“You didn’t tell anyone else besides the other mechanic, did you, kid?” Yamada’s strange husband continues, making Denki jump. 

He glances up to see both sets of eyes trained on him. So much for the assumption that they’d return to uncomfortable silence; this could arguably be worse. 

“No! Of course not,” Denki murmurs back, earning a tense but genuine smile from Yamada and a grunt from his partner. The two look away from him and at each other so simultaneously that it raises the hair on his arms. “I didn’t want to alarm everyone, erm, just in case it somehow is a dumb prank left behind by someone else, which would be really shitty by the way, not that I think it’s a prank or I wouldn’t have asked for you, it looks very real, b-but I could be wrong ‘cause I’m not expert, a-and if so I’m really sorry for wasting your time—”

“Kaminari,” Yamada interrupts, and - wow, he didn’t think the professors even bothered to learn the names of the support staff. The man flashes another smile at him, this time with teeth. “Take a deep breath for me, will ya, listener? Even if it is a prank, you’re not in trouble! And I’m sure we’ll get a good chuckle out of it, won’t we, Shouta?”

‘Shouta’—Kaminari is almost positive that’s a given name and won’t dare use it—grunts again, gaze once again levelled on the machinery and open pool of water in front of them.

The bright yellow upper casing of the sea-rover breaches the surface.

Denki starts to rise from his chair, preparing to wrangle the device into position, but Yamada waves him back down and takes over the task. The rover itself is compact, roughly the size of a minifridge but capable of propelling itself unassisted through the water and sturdy enough to hold up at depths far deeper than it’s been used for thus far. It’s kind of Denki’s pride and joy of the expedition, so he has to bite back a grimace each time Yamada bumps it into the pool’s sides. 

Finally, it’s able to be hauled straight vertically, and Denki sees a first flash of vibrant color from the netting below.

He really does struggle out of the chair then, but ‘Shouta’ beats him to it, double-fisting the net and yanking it around for a clearer view of the shape inside. Denki can’t see past him, but he takes notice of the man going stock-still and the hissed ‘Fuck,’ that follows. 

Denki’s throat is dry. “What can I—”

“There’s a divided holding tank in the room next door. Get it filled from the external pumps.” The man swears again under his breath, struggling momentarily to unclasp a key from the ring on his belt before shoving it in Denki’s hands. “Don’t say a word about this to anyone you see. Do you understand?”

He can’t help himself; he stumbles sideways and catches a glance of greyish-lavender skin and purple neck gills that are fluttering, moving , oh shit it’s really alive — “Y-yes, mister… Yamada?”

“Aizawa,” the man corrects, hauling the netting further up until a breathtaking dark tail bumps the pool’s edge. “Any day now, kid, get a move on!”

The pain is a distant thought as Denki lurches from the room, leaving the pair to their agitated whispering. Footsteps thunder down the hall from the opposite direction and Denki nearly runs headfirst into Bakugou. He must be wearing quite the expression, because his colleague’s eyes inch wider in understanding.

“The—the tank, we need to fill the tank,” he stammers out, brandishing the key and motioning to the next door along. 

Bakugou nods wordlessly and grabs it out of his hand, easily beating Denki to the door and swinging it open. The room beyond at first looks like a storage room, with all manner of boxes and doodads piled about carelessly, but the truck-sized glass enclosure against the back wall is impossible to miss.

“Stay the fuck here, you’ll trip on something,” Bakugou growls, pushing the key back at Denki before maneuvering his way through the mess to the tank’s valves and control panel. One jarring pipe-squeak later, seawater slams into the interior glass wall, brown-green and frothing.

Not wishing to be entirely useless, Denki starts shoving aside the lighter objects littering the floor, clearing a path to the tank’s stairwell.

It feels like eons before there’s shuffling in the hall and Aizawa shoulders the door open and backs into the room, arms full. Denki scrambles out of the way and watches in mute awe as the man wrangles the upper half of a near-motionless form through the doorway, followed by Yamada who is barely keeping a grip on a long, thick tail. 

“Holy fuck,” Bakugou chokes out, and Denki nods in agreement.

Denki’s no expert on mer, but he’s pretty confident that this one’s male, if there’s anything to be said for likeness to humans. He resolves to look up some more specific shades of purple because from horns to tail there’s no better single adjective to describe the fella. Right now, however, the hair that looked so ethereal on the rover’s camera drips down over speckled cheeks and long ear-fins, blackish lips part soundlessly with gills bubbling out air, and blood drips from a series of gashes on his bare lavender chest.

The two men struggle to climb the tank steps with their burden, which is hardly surprising; the merman’s waist to tail alone must be six feet at least. Then, Yamada falters on the second-to-top step and accidentally pinches a pelvic fin against the metal railing—

And the merman explodes into movement, letting out an ear-piercing shriek. He writhes against his poor handlers, throwing what must be hundreds of pounds of scale and muscle back and forth. Denki can only watch and call out a warning as Bakugou scrambles up the steps to help, and the next moment a railing clatters noisily to the ground, and—


He’s showered with droplets even from several feet away.

“Bakugou!” Yamada shouts.

The scene in the tank is chaotic, six limbs and a tail and too much splashing to make any sense of what’s going on. Bakugou’s strong, he knows, and thankfully there wasn’t yet enough water in the tank to reach past the other blonde’s shoulders when standing, but still — Denki’s pulse hammers in his throat and he hobbles for the intake valve just in case.

When he looks back, Aizawa is leaned half into the tank, one hand tangled in a cloudy mane of purple hair which he holds against the glass just under the surface. The merman’s lips are pulled back in a wordless snarl across bared shark-like teeth.

Bakugou is standing on the opposite side, shoulders hunched and covering one of them with a hand. “The asshole bit me!” he roars between coughs. “I saved you, you stupid fishy fuck! Bleed out for all I care!” He edges toward the tank wall attached to the stairs, but rethinks it when a rumble echoes through the water and the merman’s tail thrashes.

There’s a knock at the door. “Hello? Is everything alright in there? I was passing by and couldn’t help but overhear… is there an injured fish…?” Uraraka’s worried voice trails off.

Denki looks to Yamada for guidance, who looks at Aizawa, who drops his head in defeat. Bakugou at least has the sense to look guilty, murmuring something along the lines of ‘at least she’s a vet’.

“Uraraka, do you happen to have any medical experience with humanoids, too?” Yamada calls out.

“Um? I have b-basic first aid training, and then a bit more, but I can go get the doctor if someone is badly hurt—”

“No no, you’ll do!” Yamada squeezes the bridge of his nose. “We’re going to let you in, but you mustn’t speak a word of this to anyone else, alrighty, listener?”

“O… kay?”

Denki takes a deep breath, heads to the door, and pulls it open with a half-apologetic smile. Then he steps aside.

Stepping in, Uraraka flicks her gaze between the group of them before finally landing on the tank. “Oh," she says weakly, hands going limp at her side. "Oh my god.”

"If you don't mind," Yamada continues with a brilliant smile bordering on manic, "Would you quickly go fetch your medical supplies? The water's color is growing alarming, and we can't risk losing a mechanic."

As if on cue, Bakugou sways against the glass inside the tank.

"Oh my god, w-what?!"

Chapter Text

It takes three of them in the tank and Aizawa still hanging over the edge to keep the merman still enough to be worked on — and really, they only manage it when he drifts back out of consciousness five minutes into the whole ordeal, falling limp against the glass.

In those five minutes, Denki realizes three crucial things:

Firstly, no, merfolk don’t understand Japanese. As the only one not in the tank in some capacity, he mumbles reassurances through the glass, watching the alien face on the other side contort with all manner of pain and panic. It’s only when Aizawa snaps at him that Denki falls silent and watches with a sense of helplessness.

Secondly, the merman has a surprising number of natural weaponlike advantages, and doesn’t hesitate to use them. Even with Aizawa holding its jaw shut and keeping those terrifying teeth away from the three in the tank, it turns out that mer have literal claws for nails and the stiff sections of their fins are sharp enough to cut if touched the wrong way. That’s to say nothing of the six feet of muscle in the tail, which Bakugou fights to keep pinned against one wall with a grimace. Those handling him will all need a few bandages from the first aid kit, judging by the yelps and swearing.

Thirdly, this mer is, more specifically, a siren.

There’s a moment near the end of the struggle that even minutes later Denki only remembers through a cloud of fuzzy feelings; Yamada had finally captured both the merman’s wrists, allowing Uraraka to move in and do a cursory check of the wounds. Denki recalls its face then, ear-fins pressed back and dark sclerae visible all the way around lavender-pink irises. With one desperate yank, its jaw came free of Aizawa’s grip, and—

let go - settle in - fall asleep - drown - drown - drown

“No you don’t, goddamn trench gremlin, let them go— fuck, Hizashi, stand up!—Hizashi!”

There’s a renewed series of splashes and Denki feels the glass shudder against his cheek. His cheek? He blinks and finds himself pressed to the tank, then pulls away to see Bakugou, Uraraka, and Yamada all pushing their heads back above water with wet coughs and gags. The two around his age look dazed and bewildered, but Yamada stares at his husband and chokes out, “Never thought I’d experience that again!”

Aizawa’s too busy strangling the siren to reply. 

When the creature finally falls unconscious once more, everything goes much, much smoother. Denki’s no doctor but he helps clean and bandage the bite on Bakugou’s shoulder, then fetches an armload of towels. He drains most of the worryingly brown water from the tank and replaces it with fresh intake, listening to Yamada and Uraraka discuss merfolk biology in low voices.

Five minutes later, Uraraka pulls herself from the tank. The question Denki’s wanted to ask since spotting the body on the rover’s feed pushes itself past his lips at last: “Is he going to be okay?”

She gives him a slightly-frazzled half-smile. “Honestly, Kaminari, I’m not sure whether to treat him like a human or like a fish! He’s relying on gills right now, but for whatever reason, he also has dormant lungs, and... I usually only have to account for one or the other when it comes to anesthetic, you know? And on top of that, my normal patients don’t have fingers to tear off bandages with!” She worries her lower lip between her teeth, then laughs. “He’s right in front of my eyes, and I still can’t believe what I’m seeing.”

Denki looks past her to the prone purple form, stepping closer to the glass once again. Out cold, with relaxed features, the siren’s face made a breath catch in his throat. High cheekbones with small scales speckled across them, a smooth jaw, strange dark lips parted to show only the tips of pearly triangular teeth. Even the mottled skin reminiscent of bags under his eyes feeds into the otherworldly visage unlike anything else Denki has seen.

Pushing his own bangs back from his face with a sigh, Denki murmurs, “He’s gorgeous.”

“Isn’t he?” Uraraka pulls her wet hair back into a short ponytail. “Professor Yamada said that’s part of a siren’s danger. And that song of his… I’m going to grab some MS-222 and pray that we can keep him out that way. You and Bakugou don’t need to stick around for the surgery. I’m sure you’ve got work you need to get back to!”

Denki checks his phone. It hasn’t even been an hour since he first spotted the siren. He can’t even imagine busying himself with anything else at the moment.

Yet Yamada still hurries him out of the room as soon as Uraraka returns with the anesthetic, suggesting he take a breather and grab a bite to eat, because the siren isn’t going anywhere anytime soon and is in good hands. Yes , he can come back later, but please keep it hush-hush for the time being, alright?

Which is how he finds himself sitting in silence in the mechanical bay with Bakugou, neither of them more than a few bites into their sandwiches, unable to focus on his literal job in favor of staring blankly at the floor.

“What’s all the secrecy for, d’you think?” he finally works up the nerve to ask the other blonde. “I mean, this is big , we might be the first to see a live mer in centuries, shouldn’t we be celebrating the fact that they’re not all gone?”

Bakugou doesn’t respond at first, brows knitted. After nearly a minute, he growls, “You know there’s more than just magizoologists and historians on board, yeah?”

“Well, yeah.” RV Shinkai Maru isn’t anywhere near the largest ship in the agency’s fleet, but there’s at least a dozen established researchers and instructors and roughly the same number in interns. And that’s not counting the support staff like himself and Bakugou, responsible for keeping the marine technology working. The three-month expedition to study the ecosystem and history of the Ogasawara Plateau had drawn all sorts of interested parties. Including questionable outliers like Yamada’s husband, who Denki’s still convinced is neither a scholar nor scientist, but whatever.

Denki vaguely remembers some of the other professionals on board from boarding day a few weeks back, but their names and studies are all muddled in his brain. He likes to stay out of their way for the most part. He’s never had much to contribute to the kind of conversations they steer him toward, unlike Professor Yamada, who is as easygoing as they come. 

“I’m not sure what you’re getting at,” he admits at last, smiling in apology.

Bakugou rolls his eyes. “Why’m I not surprised? Listen. For someone like the parakeet, who focuses on the history of the fishfucks, it’s in his best interest to get along with the purple asshole and find a way to earn their trust, right? Because the fish-people ain’t stupid, there’s no way they don’t know we’ve been looking for them. So they’re staying away for a reason. He prolly wants to release the fish as a show of good faith or some shit. Repair the relations for the long run.

“But then you got some people on the ship who would give an arm and a leg to study a live fishfuck, keeping him in captivity ‘cause that’s the only way they could stop ‘em from pulling another vanishing act. Worse, some are here for the rumoured dormant ley-line under the plateau. They’re magic-hungry and their sponsors have deep pockets. Who’s to say they won’t jump at a chance to use the purple fuck to find it? You know what the parakeet always says.”

Denki swallows. “Magic calls to magic.” He looks down at his hands. “I guess I get it. But I find it hard to believe that anyone here would lock him up like an animal.”

“Well, believe it,” Bakugou counters, swinging out of his chair and stalking to the door with hands shoved deep in his pockets. “To some people, they are animals.”



Denki lasts an incredible four hours before his mixed curiosity and anxiety demand he go back and check on the siren.

To his surprise, Bakugou is just leaving, and casually tosses Denki a key as he passes. “Fitted it with a new lock. Don’t fucking lose it, Creaky.”

Denki sticks out his tongue at the other boy’s back and bends his left knee; okay, the support brace is getting a bit noisy again, but he’s pretty sure Bakugou would stick to the nickname whether it was well-greased or not. He puts it on his mental to-do list and makes his way inside.

It’s slightly more organized than earlier, with a better path laid out and a space cleared for a table and chairs. A small blue radio is playing—perhaps unsurprisingly—old recorded episodes of Yamada’s Mic at Seaside Radio , which creates a cheerful atmosphere that’s very at odds with the rest of the room. 

The siren is, as expected, still in the tank (Denki adamantly refuses to think of it as his tank, as that would imply some sense of belonging there, which doesn’t sit at all well in his gut). He’s partially suspended in a medical hammock, just as unconscious-or-asleep as he’d been when Denki left. Now, however, there’s large blue plastic patches across the mer’s chest and abdomen, covering the stitched wounds. 

Yamada and Aizawa are off to the side at a large folding plastic table, and not wanting to disturb their discussion, Denki shuffles his way to some of the plastic chairs nearby, only just able to hear what’s being said. Yamada gives him a short smile and wave, likely pointing out their guest, and both straighten up.

“So I think it would be best if we keep him onboard for a while,” Aizawa drawls.

No. No no no. Denki lurches up again, ignoring the stabbing pain in his heels. His conversation with Bakugou comes back in a rush. “You can’t!” He swallows when Aizawa raises a thin eyebrow at his outburst. “I-I mean. He’s not an animal, you can’t just cage him and study him and--”

“Oh, Kaminari, no,” Yamada says, voice gentling. “That’s not what Shouta is suggesting at all! Neither of us want to see him as a captive. It’s…” he looks at his husband. “...for his own safety. And somewhat difficult to explain...?”

“Try,” Denki snaps back. “Please.”

To his surprise, it’s Aizawa who sighs and waves him over to the folding table. A partial map of the Pacific is unfolded, marked with the major local trenches and the Nanpou Islands. A red sticker marks their current location on the Ogasawara Plateau. There’s also a strange white object not unlike an arrowhead, sharp on one side, which Aizawa retrieves and holds up between them.

“First of all. This was found lodged next to a rib inside one of his wounds. It’s likely the only thing that stopped him from bleeding out before your camera picked him up.” Up close, the polished stone—or is it shell?—looks sharp enough to cut, like a fragment of a knife. “It’s part of a weapon, not unlike the kind that have turned up in past archaeological digs at known merfolk civilization sites like the one we're parked over. And, by extension, it implies not only that there are others in hiding, but that he was involved in a scuffle that should have killed him.”

“That’s not too hard to follow,” Denki says. Fascinating and worrying, yes, but complicated? Nah.

“I would hope not. But mer don’t attack their own without trial, and on top of that, there are no modern settlements on the plateau—it’s not a matter of them being hard to find, they just don’t exist. That’s why Hizashi’s here. To study the history of them in the area.”

He can’t help it. “And you?”

Aizawa’s gaze narrows. “Irrelevant to this explanation. As I was saying, mer are no longer here. So our friend in the tank must have drifted while injured - from the south, with the current. Our guess is from one of the trenches.”

A wisp of a memory, foggy but still there, hits Denki—’ No you don’t, goddamn trench gremlin, let them go’— and he frowns. “But you knew that earlier, didn’t you? Back when he had us under his song.”

It’s just a flash, but he swears Aizawa’s features pull into something resembling alarm for a split second. “You—hm. You weren’t underwater,” the man grumbles slowly. He glances over Denki’s shoulder and makes a sour face. “Yes, well. I had my suspicions. Sirens in our waters historically kept near trenches.”

It doesn’t feel like the full explanation, somehow, but the dark expression on the man’s already-intimidating face has Denki dropping that line of questioning. “So you want to keep him on the ship because it’s far from his home?” Then more of the puzzle pieces clicked. “Oh. And he might not be welcome back.”

Aizawa gives him a long, tired look. “I’ve no intention of keeping him for an extended period against his will. He’s not a prisoner. But first he should heal where nobody else can take advantage of his current state.”

Denki nods, but can’t push away the nagging worry at the back of his brain as he turns and looks at the stunning, sleeping creature in the tank. And then what?  

He rubs at his arms, a nervous habit, and approaches until he can lean against the glass. It’s cold and uncomfortable but grounding, in a way giving more substance to the seemingly impossible last few hours. 

It’s almost silly, he thinks, how terribly concerned he is for the mystical figure within, who is no doubt far stronger and more capable than Denki himself. Strange, how attached he is to the wellbeing of this stranger he’s never shared a conversation or meaningful exchange with. Pitiful, how desperately he wants for the siren to open those beautiful, alien eyes, and be okay.

He’s pulled out of his thoughts by the scrape of a plastic chair on the ground right beside him; Yamada had carried it over. The man grins. “You look like you’re going to stick around for a while. Best to be comfortable doing it.” Then he holds out a hand. “Can I give you my number? I’d like to know when he wakes up, and it will save you having to search the ship for me again.”

“Uh, y-yeah, that probably makes sense,” Denki mumbles, handing over his phone on the ‘new contact’ screen. He’s quiet while the information is entered, repositioning the chair so he can tilt his head back against the glass and use the light from the tank to do his work. Before the men reach the door, he speaks up again. “E-even if he has nowhere to go... I don’t want him to be stuck here, or studied. That’s…” he swallows. “That’s wrong.”

Yamada smiles at him warmly, eyes crinkling and almost teary as he nods. Aizawa huffs out something that’s barely passable as a laugh. “Kid,” he says, turning away. “We’d never let that happen.”



Denki wakes up to the sound of his workbook sliding off his lap and slapping the floor.

The radio’s still going, but now there’s a light blanket draped over his shoulders which he’s confident was not his doing. He shrugs it down around his elbows and leans forward. On a second plastic chair beside him sits a covered plate of food and a pink sticky note that reads ‘Some nourishment for the ship’s best babysitter! (•̀ᴗ•́)و  -O’.

He rubs his face and laughs, arching his back until it clicks pleasantly. Of all things to bring him closer to the others on the expedition, he wouldn’t have expected a mythical creature to do the trick. 

Speaking of. He lets out a breath and glances over his shoulder into the tank he’d been sleeping against so soundly.

And is met with a pair of open eyes, lavender on black, and an otherworldly face less than a foot from his own.


Chapter Text

Denki startles violently, lurching away from the glass.

“O-oh fucking heeelllllllllllo, hi there buddy, alright wow yes hi.” He puts all of his functioning brain cells to work on simply not falling out of his chair. His heartbeat hammers at top speeds, a conflicting blend of panic and awe zipping through his veins.

Having also recoiled several inches at Denki’s flinch, the siren watches at him warily, upper lip drawn back over predator’s teeth.  His ear-fins flick and pin back, shoulders rising  and tail lashing against the far side of the tank with a resounding thud. The medical hammock, still fastened on one end, rips and drifts listlessly towards the tank’s filter; when it brushes the siren’s side, he jerks away and an unmistakable wince crosses his face.

Denki struggles to his feet and backs up hurriedly. “Hey, hey, no, it’s fine, you’re fine, I’m sorry I just wasn’t expecting—” He swallows. Sure, the fella can’t understand him, but there’s something to be said for tone and body language, right? He clamps down on the shrillness in his voice, forcing it to steady. “Look, see? We’re good, you ‘n me. Let’s just take deep breaths—or, um, whatever it is you do with gills—and neither of us freak out so you don’t aggravate that side of yours.” He dons a toothy smile, then thinks better of it and closes his lips.

After the surgery one of the others must have finished filling the tank to the standard capacity to give the siren more room. Now, as the long-bodied figure looms in the upper half of the enclosure’s waters and glares down, torn fins flaring out like the corners of an extravagant cloak, Denki feels smaller and less impressive than ever before.

“Y-you’re incredible,” he mumbles. The hair on his arms stands on end. “Like, damn. You can’t understand a word of this but I want you to know I’m… I’m on your side, as much as you’ll let me be. Which is probably not at all, considering, well.” He waves vaguely at the tank, swallowing. The siren is still guarded, which twists Denki’s innards with guilt, as if this whole situation is his own doing.

And really, that’s not too far off the mark, is it?

He rubs at his arms, but still can’t bring himself to look away. At least his rambling seems to have eased some tension from the other being. Those stunning eyes, while still filled with distrust, are scanning him up and down and flicking around the room.

Denki chuckles weakly. “Yeah it’s… nothing special, sorry. I don’t think this room’s been used yet this expedition as anything other than storage, but you’re safe here. At least until we can release you, which we are going to do as soon as we can, once you’re, uh. Once you’re better.” He motions to the blue plastic bandaging on the siren’s chest, then pats the same place on his own. “How’s it feel?”

The siren lays a hand over the bandage with a scowl and angles that side of his body away from Denki, gaze narrowing. He doesn’t make any move to tear it off, though, which alleviates some of the concerns Uraraka had expressed.

Oh—he was supposed to alert the others when their patient woke up, wasn’t he? Denki pats his pockets for his phone, then spots it clattered on the ground near his workbook, along the base of the tank.


The others can wait a bit longer.

“I’d ask if you have a name, but I doubt that’ll get me very far. Maybe I should ask Professor Yamada if he has any texts I can borrow? But for now, uhh. Den-ki.” He points to his chest. “Den-ki. Denki.”

In a kinder world, maybe the siren would now be trying to imitate the sounds like a curious toddler. But in reality, Denki’s just given an increasingly suspicious look before the siren starts tracing the edges of the intake vent, trying to wedge the ends of his claws under the frame.

Denki hobbles forward again, one slow step at a time. “Aw, don’t take that apart, my guy, I can’t get in there easily and you’ve already done a number on Bakugou’s patience. And it’s either this tank or you working out those lungs you apparently have and chillaxing out on the floor, because there’s nowhere else we can put you where you’re safe from prying eyes, y’know? The others onboard won’t have as much reason to question why we’re bringing buckets of fish in here or anything either, as compared to like, the barracks. Wait, do you even eat fish? Was that insensitive? I mean I don’t know what other options you’ve got down there, and with chompers like those, er…”

He trails off, having earned the siren’s attention once more. Over the years, many people have groaned, rolled their eyes, or snapped at him to shut up—Bakugou even throws wrenches—so Denki’s aware that his word-vomit style of rambling isn’t for everyone. It’s just as much of a nervous tic as it is an excited one, and right this moment it could easily fall into either category.

So when the merman’s expression morphs into one of exasperated perplexity—a response so wonderfully familiar —Denki flushes pink and bites his lower lip in a failed attempt to stop the gooberish grin that pulls across his face. He covers his mouth at the last minute to hide his teeth, which only serves to make the siren look even more confused.

Then Denki gets yet another shock when the siren opens its mouth and murmurs back.

His language is like the sloshing of a stream over river rocks, filled with warbles and hisses and clicks. It’s a short phrase, whatever it is, muted by the water and tank wall separating them. But the smooth, deep voice washes Denki with shivers and sends his pulse thrumming once again.

He limps forward, fingertips dropping from his face to press gently at the glass. “So freaking cool.” Then he taps his chest again insistently. “Den-ki. Denki. That’s my name. Denki.”

The siren sinks down to almost eye-level and keeps watching, thick tail coiling against the back wall of the tank. The wariness hasn’t left his features but it’s less acute then before, evident only through the shallow squinting of his gaze.

“We’re gonna be bros, just you wait,” Denki says. “I’ll keep you company and talk your ears off ‘til you get better! O-or until you’re sick of me, er, whichever comes first. I still gotta work but I can get away with doing some smaller projects in here, and… oh! Man I’ve got so much shit that’ll blow your mind! Then you can say you met this cool human dude and—” his smile falters. “And, well, that’ll be that.”

That’ll be when the siren disappears beneath the waves again, possibly cutting all contact with humanity for another century or more. And that’ll be when Denki loses his ‘best babysitter’ status and goes back to being the expedition’s more forgettable technician, unable to speak a word about this whole experience.


He only realizes he’s chewing on his lower lip when the siren moves closer and stares curiously at his mouth. Denki’s about to stop when the other opens his jaws—but there’s no aggression to it.

The siren runs a purple-grey fingertip along the points of his own fearsome teeth, poking out from behind dark lips. It’s almost as if he’s… comparing them.

A thrill comes over Denki and he grins again, this time not hiding it. This is wild, what they’re doing—such a simple exchange of information, and yet it feels like so much more. “Shit, yours are way better! I’ve only got a few sharp ones but they’re wimpy in comparison. And one’s chipped, see?” He holds back his lip briefly, then laughs. “I, uh. I fall down a lot. Gravity’s a bitch. I’d say legs are overrated but my sample size has left me a bit biased, it’s hard enough to climb the stairs to the mess hall most days.”

The siren squints back at him, mouth quirked to the side, fingers curling against the glass. The guy may not be a conversationalist, but at least he’s a good listener... even if the words only come across as meaningless babble.

Denki finger-guns at him to battle back the mild disappointment. It earns another confused look.

When his phone pings, both of them flinch, and Denki snatches it away from the base of the tank. It’s only one of his gaming buddies sending a meme, but it works well enough as a reminder. “Here I am running my mouth when there’s others that might know a bit more on how to talk to you, jeez. If I’ve been stumbling my way through with one social faux pas after the other, I am so sorry, for real.”

He pulls open the contact for Yamada Hizashi and starts the conversation:

professor yamada? it’s kaminari

he woke up

The reply is almost instantaneous.

Brilliant! We’re on our way!

Denki glances up at the siren, who is watching the phone with rapt fascination if the slow spreading of his ear-fins is anything to go by. He desperately wants to pull up a YouTube video to see the sea-dweller’s reaction to moving images, but shelves that for later. 

For now, he’s internally mulling over the best way to herald the others’ arrival. Sure, it’s silly and illogical, all considering, but whatever. He settles on pointing to the door and gestures a ‘come here’ motion at it, keeping eye contact with his companion.

Not moments later, it creaks open. In the brief pause where Denki turns to look, there’s a quick splash, the merman propelling himself away with tension lining his frame once again.

"Hey, no, it's okay my dude, they're good," Denki says, leaning into the glass with a sigh.

From across the room, he hears Aizawa mumble to his husband, "Kid's still trying to make fruitless conversation, I see..."

But Yamada isn't paying him any mind, staring past Denki with a near-reverent smile. “Oh my stars! Look at you." His voice is softer than Denki's ever heard; he slowly approaches the tank with his hands low and palms open, facing forward. "Strong one, aren't ya, to be moving around like that so soon? You'll bounce back from that injury in no time. But what did you get messed up in that put you in our path to start, huh?" 

Denki raises an eyebrow at Aizawa—You were saying? —to which he recieves a scowl in return.

When he looks back into the tank, he finds that the siren's gaze is jumping between all three of them, but unquestionably resting the longest on Denki's—as if looking for answers. 

"Looks like you two hit it off well," Yamada says, but this time he too is facing Denki with a curious grin. "Nothing wrong with that. If his fin and horn development progress are to be believed, you're in the ballpark of the same age! Or... same stage of maturity, at any rate." He winks, and Denki's about to ask what that means when the man casually slings an arm around his shoulders and grins at the siren. "You must be getting hungry! Don't worry. Kaminari's going to stick around for a little while longer, isn't he?"

Denki nods quickly. "Y-yeah, of course."

"Great! Fantastic! What better way to bond than a shared meal, right listeners?"

Aizawa trudges to the base of the tank stairs, ignoring the warning hiss from the other side of the glass, and drops a bag near the bottom step. It squelches upon hitting the ground. 

He then meets Denki's gaze. "Well, kid?" Denki swears there's a hint of a smirk on the dark-haired man's lips. "Suppertime. You're up."

Yamada throws his head back and cackles.

Denki regrets everything.

Chapter Text

Denki’s been an advocate against stairs of all kinds for over half a decade now, but rickety metal steps that clang with each footfall have always been on his shit list. Add a pit of water to one side—complete with a wary being capable of mind control—and suddenly he’s sure that there’s a serious Health & Safety violation complaint to be made here.

His leg braces may be advertised as lightweight, but he still struggles with each step, leaning heavily on the questionable railing opposite the tank. He takes some solace in Aizawa’s presence only a few steps behind him, close enough to prevent him from tumbling the dozen-odd feet to the floor. Or into the tank itself, should the siren get any ideas. Still, they’re putting a great deal of faith into his donned life jacket, he thinks.

Denki casts a glance into the water; a long purple blob sits on the opposite side of the tank. The merman’s eyes seem to glow, cutting through the green-brown seawater from a distance. Watching.

Taking a deep breath, Denki tosses down the cushion Yamada had provided and carefully lowers himself onto it, one leg over the top step and the other bent awkwardly in the direction of the tank. This leaves enough room for Aizawa to lean over him and drop the duty bag on his other side.

Then the disheveled man abandons him, returning to where Yamada is sitting near the table to watch the whole affair.

(“You’ve managed to build the most trust with him,” the researcher had said, when Denki first protested the additional duties of his babysitter designation. “If I go up there he’ll have me in that tank in an instant!”

“What about Mr. Aizawa?” Who should have been the first choice, in Denki’s opinion, what with his inexplicable resistance to the siren’s song.

Yamada’s wide grin had flickered almost imperceptibly towards a grimace. “Falling in the water would be even worse for him! He reacts to the salt dreadfully, even in short doses.”

Denki looked at Aizawa, who must have heard, as he lifted one arm with an irritated sigh. The arm that he’d plunged into the tank to steady the siren’s jaw – now covered in bandages from finger to elbow.

Well, crap.

“Okay,” Denki said, swallowing. “Fine, I’ll do it.”

“Atta boy, Kaminari!”)   

Now, he shakes his head and reaches for the zipper to the deep blue bag, dreading the contents. He feels like a horror movie protagonist as he pulls it slowly down the row of teeth…


That was the squelch.

“You guys did see his teeth, right?” Denki mutters just loud enough to reach the men sitting more comfortably below. But he’d spoken too soon; next to be revealed is a plastic container filled with foot-long slices of meat, and beside that, an entire softshell crab. “Is this really the kind of thing they eat?”

“Well… not exactly,” Yamada chuckles. “But we’re in no position to fetch deeper-sea eels and crustaceans. So local substitutes will have to do! It won’t do him any harm. Truthfully, he could likely even stomach many surface foods without issue – but I daresay that’s beyond his trust.”

Denki pulls some of the stringy seaweed out and looks around for somewhere clean to set it. He finds none.

Scowling, he calls out, “Man, I’m not just tossing this into the tank. That’s hella rude. Is there something down there I can use as a plate at least?”

As Yamada scouts around through the mess of objects in storage lining the walls, Denki peers into the water again. The siren has inched closer with Aizawa’s departure, but is staying safely under the surface. Those piercing eyes track the bundle of seaweed curiously.

“If this was dried, I’d be all for it, my dude,” Denki says with a laugh. “Little bit of rice, some choice salmon and roe and dipping sauce—mmm. Don’t think I could stomach it like this. I’ve got a low tolerance for food with the consistency of wet rubber.”

“Ah!” Yamada exclaims. “Will this do?” He brandishes a blinding-yellow foam kickboard.

“Better than nothing,” Denki agrees, catching it when it’s tossed. He dusts it off with his sleeve and settles it in his lap, then places a wad of the seaweed to one side, aware once again of the siren’s gaze on him. “Prepare to be blown away by my unparalleled plating skills,” he jests, making a show of arranging the aquatic plant in half-hearted spirals. Then he reaches into the bag for the crab.

Halfway to the kickboard, it splays its legs all at once - and Denki flings the still very goddamn alive what the fuck crab with a shriek.

It hits the water with a small plop , and then there’s a rush of movement and a crack against the glass below that shakes the stairs. Denki glances into the water and first sees only an array of purples, until he spots two strong hands, holding—crushing —the twitching crab against the side of the tank.

The siren’s face turns upwards, meeting his stare, and Denki sucks in a quick breath because holy shit he’s so close, within an arm’s length, so vibrant and wild and… dangerous. All the siren has to do is reach up, and…

“Back up, kid,” Aizawa calls out, likely on the same train of thought.

Denki lurches back from the side, sitting once again against the railing of the stairs, trying to calm the frantic stuttering of his pulse. He holds the kickboard between them as if it could offer any protection.

“Y-you could have warned me that it’s alive,” he gasps out, then corrects: “Was. Was alive.”

“As I understand, it moving should have been warning enough,” Aizawa drawls back. “If you weren’t distracted trying to impress your charge, perhaps you would have noticed that.”

Denki’s ears burn at Yamada’s subsequent hyena-laughs, and he pettily turns his back to the men, trying to salvage his pride simultaneously with the skewed seaweed pattern on the kickboard.

He twitches when the tip of two horns break the surface a few feet away, followed by the upper half of the siren’s face, forehead plastered with wet aubergine locks. Those dark sclerae make it look like the mer’s lavender-pink irises float in ink, and give an impression of pinpoint intensity far beyond anything a human could muster.

“S-sorry, uhh,” Denki says, re-balancing the makeshift plate. He eyes the dangling crab body clutched in the siren’s hands. “Don’t worry about giving that back, I’m not sure it’ll add much to the plate at this point.”

The foot-long slices of eel meat are, to his surprise, cooked – much the same as he’s used to finding in his own dinners. He’s not actually sure what eel looks like raw, especially not the deep sea varieties, and the merman looks mildly wary of it. Denki places two of the sticks on the board regardless.

Then, very carefully, he leans over just enough to place the floating ‘plate’ on the tank’s surface, and taps it gently in the siren’s direction.

“Bon appetit, buddy,” he mumbles with a nervous smile.

The other drops back below the surface.

Denki thinks, for a moment, that despite his best efforts he has royally fucked up and managed to offend the guy. He’d practically chucked half the meal at his charge’s head with a banshee scream, after all, and can’t begin to imagine what kind of interpretation was made from that. He’s got an apology ready to roll off his tongue when a clawed, webbed hand slides over the opposite side of the kickboard and drags some of the seaweed back down under.

He leans back with a relieved sigh. Done and done. His own stomach gurgles weakly, but least he wouldn’t be responsible for starving a beautiful, mysterious mythical creature. “Is my meal from Uraraka still down there, or should I resign myself to his diet, too?”

Aizawa fetches the prepared human-food plate, and for the next half hour the room is surprisingly peaceful. Denki lets his mind drift to the tank filter’s low humming and snippets of murmured conversation down below. When gentle snaps and crunches start from within the tank, he adamantly looks away and sets aside his own plate with a grimace.

The cooked eel, however, remains untouched. The next time Denki sees the grey-purple hand feel across the surface of the board for seaweed, he grins. It’s all gone – save for the stuff still heaped in the duty bag – and when the siren’s head finally breaches it’s all he can do not to snicker at the way the mer glares at the offending meat.

“C’mon, give it a try! May not be as slimy and alive as you’re used to, but it’s really good, promise,” Denki assures him. When the siren doesn’t react to that—because really, why would he?—Denki mimes picking it up and taking a bite, then smiles theatrically.

The siren squints at him, and roughly nudges the board back toward the stairs. Seawater sloshes over the meat as it bobs its way back over.

Denki sighs and unzips the bag—

take it – bite –

He tastes salt and smoke, wanting to gag at the unexpected food on his tongue but not able—

chew – swallow

He’s aware of his teeth gnashing the eel meat that the siren has fed him with Denki’s own hands, and as cloudy as his brain feels, each thought struggling through fog, he’s distantly grateful that the merman has taken his stubby grazer’s teeth into consideration.

Denki feels himself swallow, and his mind clears.

“Uurk,” he groans, wiping away the salt water and juices on his chin with the back of his hand. “No, buddy, no. That wasn’t very cool.”

A squeeze on his shoulder alerts him to Aizawa at his side, looking equal parts irritated and concerned. “You good, kid?”

Denki slaps the eel slice back down on the kickboard. “Just dandy. Would have been nicer with rice. Or if it wasn’t drenched,” he grumbles. He tosses the makeshift plate back into the tank, glaring at the partially-surfaced mer, who doesn’t look apologetic in the slightest.

However, as he watches, a hand slowly snags the bitten slice and drags it down.

When the meal is over, the siren resurfaces, seemingly content to listen to Denki talk. And Denki does talk, explaining the purpose of the expedition and what kind of duties he has, recounting the first time he’d controlled the rover and how mind-blowing and unnerving he’d found the vast open world beneath the waves.

He chatters about his coworkers and the interns he gets along with; of how Bakugou threatened to toss him overboard on an hourly basis the first week, until they learned each others’ boundaries and Denki realizes that giving Bakugou the larger-scale engineering jobs was easier on the both of them. He laughs about Uraraka slowly claiming parts of the mechanic bay as a place to relax and talk shit at Bakugou; the two of them are practically competitive about it.

Denki’s met a few of the other interns at mess, too, and counts the names he remembers off on his fingers. Yaoyorozu, working on her Theory of Magic doctorate, Kouda and Tokoyami, in zoology, Iida in history. Then he recalls one of the interns he remembers on the basis of dislike: a loud Applied Magic student who’s always showing off and badmouthing the magically-inept—Denki’s somehow managed to avoid his jeers thus far.

He’s not sure how long he goes on; time falls away, and it’s surely getting late. His back and hips start to ache from the cold, tough metal behind and below him, and he adjusts his position with a wince. He’s not doing his already-fragile lower joints any favors sitting up here when there’s actual chairs down by Yamada and Aizawa.

His left knee spasms when he straightens it across the stairs, telling him yeah, it’s time to get down.

“Gonna get to ground level and then we can continue this fantastic dialogue, alright?” he says, easing both legs around.

The siren drifts closer, still submerged from the nose down, and slowly curls the fingers of one broad hand over the edge of the tank. His dark claws click against the glass, and the sound casts a shiver down Denki’s spine.

“Erm, Mr Aizawa? Could I get a hand down, please?” It’s not that he’s afraid of the siren, per se—he’s moderately confident that the big purple fish-guy means him no harm—but everything about him screams ‘predator’, and some primitive instinct is currently reminding him that there’s a reason so many old tales end with sailors becoming ill-fated playthings.

When Aizawa sighs and gets up, Denki gently lets his feet drop a further step down, and eases himself to an unsteady stand.

don’t go – stay with me – turn back – come here –

The cloudiness in his mind is brief this time, because it is interrupted—

By pain.

He’s yelling even as he comes out of the trance, facedown against the metal grill of the stairs. His shins throb and burn and feel like they’ve been smashed to pieces all over again, even as he casts a glance over his shoulder and sees that they’ve just hit the steps at a terribly unfortunate angle where the braces couldn’t protect them.

He leans into where one step is biting into his hip, trying to shift the pressure away. He should have just waited for help to come to him, should have ignored his flight response—they’d been doing so well.

Aizawa curses, hands held out awkwardly as if unsure of where to put them. “What can I do, kid?”

Denki chokes on a gasp and blinks to clear his eyes of unshed tears. Hopefully the men wouldn’t think any less of him for it; this fucking hurts. He struggles to turn over so at least it’s his back to the stairs. Everything feels broken, but he’s pretty sure that’s just his abused nerve endings causing a fuss. It’s not the first time this has happened by a long shot, but it’s one of the more painful ones in recent memory, for sure.

Seeing Aizawa still watching him for an answer, Denki flushes. He knows the help he needs, but it’s never goddamn easy to ask near-strangers to literally pick him up.

The man seems to understand it without words, though, and nods before getting an arm under Denki’s back and thighs. For someone so visibly unimpressive, the man has more muscle than Denki had mentally credited him with. Aizawa huffs and barely breaks a sweat as he navigates them down to the floor.

A long purple tail slides into view over his shoulder; the siren is drifting close to the other side of the glass, ears pinned and wearing an expression that looks surprisingly like regret. 

Denki can’t quite manage the reassuring smile he tries to fake.

He’s not entirely certain what the overgrown fish had meant to do, after all; he doesn’t remember feeling any particular impulse to jump in the water, just a forced desire to turn around and sit down near the edge, where the siren had perched mere feet away. It had been a distinctly different feeling to the drown command that morning. 

Black claws scrape gently against the inside of the glass. The siren’s chest contracts and something akin to a chirp echoes softly through the room, followed by few sounds that roll from that sharp-toothed mouth like a trickling stream.

Denki blinks. “Huh?”

“He’s sorry,” Aizawa mutters.

“Oh.” Then, “Wait, how do you—”

He’s settled carefully into one of the chairs, even though Aizawa’s expression implies that the man would rather drop him. “With that hangdog expression, it couldn’t be anything else.”

Okay, fair point. He smothers down the flash of anger, looking away from the siren. He gets enough pitying looks from people on a regular basis, people who actually understand what an inconvenience he can be. He dreads having to deal with it here, too.

“Hizashi went to get some ice. Do you need to see the ship doctor?”

Denki looks at his legs and carefully feels them down to the ankle; they’re marked up badly, but most of the damage is old scars and new swelling. The bruises will come later, and they’ll be terrible, but nothing’s broken.

“Nah,” he mutters. “I’ll be fine. I can walk.”


To prove a point, Denki grabs his cane and leans heavily onto it, staggering to his feet. Invisible knives dig in at his ankles and just under his knees, but he’s had worse, he’s pushed himself through more than a few bruises for the sake of his dignity.

“Fine,” the black-haired man relents, though he still doesn’t look convinced. “But when Hizashi comes back, I think it would be best for you to let him help you to your room.”

Denki nods jerkily, and spots his workbook on the floor near the tank, where it had fallen what feels like so long ago now. He grimaces, not due to its placement, but rather due to the shadow cast over it from the concerned mer in the tank. Apparently ignoring him for a minute or so wasn’t enough to make him lose interest.

He sighs and makes his way over. 

Purple-grey palms come up against the glass as Denki bends over, almost losing his balance again. He gives a small smile and looks away—


It’s quiet, muted by water and glass, but unmistakable. Caught by surprise, Denki blinks and raises his sights to the siren’s face. 

Dark lips form the same chirp-shush-cluck apology from minutes prior. A claw draws a ‘u’ shape from the inner corner of one eye, down around the cheek to the top of his cheekbone. The gesture’s meaning isn’t clear, but that’s not the important thing right now.

Denki swallows, a more genuine grin pulling across his face without his consent as he struggles to fight down the squeal of he was paying attention back then, he knows my name!  

But the siren still looks unsure, as if waiting.

“It’s-- it’s okay, buddy. You’re forgiven. Just… no more trying to make me use limbs that you don’t have yourself, huh? If we’re drawing lines for what we’re not okay with, that’s a good place for me to start.”

He hopes he can repeat that in a way that can be understood before anything else bad happens; for now, his new friend looks guilty enough that Denki doubts it’ll be an issue anytime soon.

The siren floats closer, at eye level once more. For a brief second his gaze flits over Denki’s shoulder to where Aizawa is milling about by the desk on his phone; then he leans in and taps the pad of two fingers against the glass near Denki’s chest.

“Den-ki,” he repeats, before splaying one hand over the base of his own neck, over his collarbone. What he utters then sounds like a string of soft shushes and a click, like the push and pull of a tide on sand. It’s long, five syllables at least if Denki’s parsing it right, but somehow, unquestionably, he knows it’s a name. The siren repeats it once more, expression determined.

Denki’s breath hitches. “Shee… Sheen-souhee… uh. Tohshee?” He can’t quite get the silky curves of the sound right, the cadence of the name foreign on his tongue. It’s almost definitely awkward and comically off like those videos of Americans stumbling through Japanese, but the corners of the siren’s lips quirk up and his eyes burn violet, encouraging. 

“Sheen-souhee-tohshee. That’s—you, wow. That’s your name?” He presses his fingers against the glass as he does so, mirroring the siren’s earlier gesture.

Vivid violet ear-fins spread and flutter gently, and the smile the other wears widens a fraction.

Giddy, Denki beams.

He wonders if merfolk distinguish given names from family names, because there’s certainly enough syllables to make that work. Maybe he’s not even breaking up the sounds correctly, if they’re meant to be broken up at all. “Can I—can I call you Tohs… er, Toshi?” Heat rises to his cheeks, which is silly, but it feels like he’s asking to use a given name and maybe that’s wrong of him to hope or pretend they’d be close enough for that one day, were this at all a normal situation. Bah.

The siren tilts his head, contemplating it, before responding with a minor amendment. God, everything sounds so much better coming from him.

“Hitoshi?” Another flutter of the siren’s ears. Denki supposes that must mean approval, and makes a mental note of it. “A-alright! Hitoshi. Wow.”

The room’s door creaks open; it’s Yamada, back with a pack of ice and… a familiar wheelchair. Spotting him, the blonde man half-smiles. “I encountered Bakugou on the way and asked him what might make you most comfortable. He said you left this in your workspace for when things got particularly bad.” The smile falters. “Did I… overstep?”

Denki shakes the instinctive grimace from his face and pushes away from the tank, more aware than ever of the shooting pains up his calves now that the rush of excitement is petering out. “No, that’s… probably a good idea. Thanks, Professor Yamada.”

He limps halfway to the chair before turning back. 

Hitoshi is drifting near the far side of the tank, seemingly caught in a glaring match with Aizawa. His attention snaps back to Denki the moment his hand rises, but the expression on the siren’s face has returned to neutral and unreadable.

“I’m coming back tomorrow,” Denki promises, for what little good his words do. “And the next day, and the next. I know you don’t understand me right now, but we’ll make it happen.”

He doesn’t see the knowing wink Yamada sends Aizawa, nor the defeated head-shake made in reply.


Chapter Text

As soon as Hizashi leaves with the technician kid, Shouta closes the door, breathes an irritated sigh, and turns to the tank. He’s waited over three-quarters of a day to get a moment alone with the siren, and now that the only one due to walk back in is his husband, he can finally take his chance. 

He stalks over to the tank’s control panel—feeling eyes on him—and activates the divider panel. The tank’s warning lights flash orange as an extra wall of glass begins its ascent in the middle of the tank, evenly bisecting it.

The young siren spits all sorts of curses and rude titles at him, but Shouta ignores that for now.

When he approaches the stairs to the tank, the brat does as he’d expected, fleeing to the opposite side of the divider before the new wall prevents him from doing so. It would be funny if not for the way the other’s ears are low and flat with fear. Shouta does his best to be non-threatening as he strips off his pullover. His undershirt and sweatpants can stay; Hizashi will know to bring him something fresh, he hopes.

Then, after a moment of consideration, he pulls off the bandaging on his left arm. Beneath, slate-gray skin and scales mark him like an accusation, like a fraud. He scowls at the sight, but the rest of him is going to match come the morning, so there’s no point making a fuss right now.

And when the dividing pane of glass reaches the top of the tank with a drawn-out beep, Shouta inhales deeply, forces it back out, and lets himself drop into the captured piece of the sea.

His body has gone so long without adjusting that at first everything burns . He shuts his eyes to defend from the saltwater and covers his mouth to stop himself from habitually relying on lung-oxygen. When nothing fixes itself within a few moments of submersion, a twist of dread works itself through his system; has it been too long? Has his body forgotten? Has he locked himself into—

A set of underused muscles on either side of his neck flex, nearly-invisible flaps of membrane pulling away with the movement, and finally Shouta can breathe.

In the back of his mind he feels the itch signalling that the brat is Singing at him, a desperate bid for control now that Shouta’s in the water, where the Song works strongest. Smart kid, he thinks, if a bit oblivious. He’ll let the little one off the hook for not noticing his gills due to the billow of hair currently obscuring his neck.

The other’s panic is almost palpable when he realizes the Song isn’t working. ≈Why won’t you listen? Get out and go take a dive in a vent, you squid-haired, gazer-faced, finless twit!≈

Shouta tries to blink open his eyes, and ends up squinting - they still sting. The young siren is against one of the far corners of his side, teeth bared and sporadically hissing as if he’s not capable of suppressing the reflex. Gods, the little asshole is as noisy and flighty as a coral mer, for all he looks and Sings like a trench-dweller.

≈You’re going to drown yourself, stupid walker, and your pod will blame me!≈

It takes a surprising amount of effort for Shouta to readjust to vocalizations without air. It really must look like he’s drowning at first, his lips and throat and chest all contracting in sequence while he figures it out.

The brat lets out a sharp bark. ≈Get out—

≈Ca— ergh. C-Calm down, you guppy,≈ Shouta finally answers. ≈I’m not at risk of drowning, but I’ll make note of your clearly genuine concern.≈

For a long few moments, nothing interrupts the slow bubbling of the tank’s filter. The young violet trench-dweller is still as stone in his corner.

Then, in monotone, ≈What.≈

Shouta grips onto one of the handles embedded in the back wall, using it to anchor himself in place. Two minutes wouldn’t be enough for the sea’s magic to change him - hell, two hours wouldn’t be enough - so he’s gotta make do with this uncomfortable barely-transitioned state. He curses, but it’s Japanese and comes out garbled with all the wrong sounds.

He’s already lamenting his decisions. Can’t even sigh underwater in any way that feels natural and refreshing. ≈Your shock disappoints me.≈ He raises his slate-skinned forearm, black scales glinting over his knuckles, and scratches idly at his sparse beard. 

There’s another extended beat of silence. ≈But. You’re a walker. You have walker-limbs.≈

≈Legs,≈ Shouta corrects absently, and he really does not want to go into the hows and whys of that right now. So he redirects. ≈Come on over here before you barnacle onto the glass. I’m no threat to you.≈


Shouta’s brain whirrs blanks. Did he just? Was that…?

≈Please tell me that’s not mainstream trench slang these days,≈ he grumbles. ≈Now, come here. We’re just going to talk.≈

The young one hunches, hesitating. 

Shouta wants to bash his own head against the floor, repeatedly. Perhaps he could learn a thing or two from the small mechanic’s patience. ≈You see this wall? I don’t have the means to break it. And even if I could and did, my teeth are walker-flat and my claws nonexistent. You have nothing to be afraid of.≈

≈I’m not afraid,≈ the mer mumbles, and finally floats closer to the glass. His gaze jumps between Shouta’s arm, pseudo-gills, and legs with confusion, but he still seems averse to speaking his mind.

So Shouta starts again. ≈What do you go by?≈

Violet eyes narrow at him. ≈You first.≈

≈Very well. Call me Aizawa, as your walker friend does.≈

Surprise touches the kid’s face for a flash—as if surprised Shouta had actually given an answer—then his lips twist. ≈He uses ‘Hitoshi’ for me.≈

And it’s Shouta’s turn to be taken aback. The young mer gave away his name to a human already? It hasn’t even been a full day! Even if ‘Hitoshi’ is only a fragment of it, harmless and unevokable, that’s a shocking offer of trust to a non-mer. The tiny blonde’s probably clueless.

Judging by the intensely defensive look on Hitoshi’s face, he knows as much. Shouta wants to groan and chastise the kelp-for-brains for his impulsiveness, but holds back. He’s not the kid’s sire, and doesn’t want to risk damaging their current fragile peace by acting like one. So he shoves back those instincts and resigns himself to a shallow nod.

≈Alright. I can tell you have questions, Hitoshi, and I hold a few of my own. So I propose we trade, back and forth, answering truthfully. Is that acceptable?≈

Hitoshi nods.

Aizawa swipes some of his drifting bangs out of his eyes. ≈Good. You may go first.≈

≈What are you?≈

Really, he shouldn’t have been surprised, but Aizawa had been hoping that self-preservation instincts would have struck up something more like Where am I? or even What are you going to do with me? — something important. He’d forgotten how insistent merfolk curiosity could be towards new things.

≈A lorekeeper of sorts,≈ he answers evasively, knowing that’s not what the kid had meant. ≈Plus a husband, a shoddy cook, and an individual cursed to be dragged along into complicated situations. Anything more specific is too difficult to explain to you at the moment.≈ He leans back against the glass. ≈Why were you exiled?≈

Hitoshi jerks back as if stung, face scrunching up with anger. ≈How did you—≈

≈I’m not unfamiliar with the laws in the trenches, little fish. Your injury was at the blade of another mer. You were cast out.≈ His voice softens more than he’d intended. ≈So, why?≈

The siren’s mouth is a straight, hard line for a solid half-minute, one hand coming up to cover the blue bandaging. Finally, he grits out, ≈I made a proposal that the wrong person overheard. It got back to the leadership. They called me a critical risk to their ‘peaceful’ way of life.≈ Then he sneers. ≈If by ‘peaceful’ you mean dismal for anyone lower-caste.≈

Lower-caste? Sirens had always been an inherently competitive, sly, and ambitious lot, some even harbouring malicious streaks towards humans and other mer. But Shouta doesn’t recall caste divisions; prestige was gathered in trophies and hoards. Even the more aggressive deep-dwellers would go out of their way to ensure the wellbeing of their own kind. It was ingrained in their magic, wasn’t it?

Hitoshi’s follow-up question makes Shouta set that aside for later consideration. ≈How do you know so much about us?≈

Shouta resists rolling his (still-stinging) eyes. What a fin-biter. Little shit’s getting specifically personal with his questions; that’s fine. He can play along and still keep to truths. ≈My partner is a walker lorekeeper who specializes in studying mer history and culture. I myself have an interest in protecting some of that knowledge from being lost, but also from falling into the wrong hands. I know a thing or two more than most walkers about sea magic.≈ He scratches his gray forearm idly. ≈Also, you are not the first siren I have met.≈   

Perhaps that last was a bit too much; Hitoshi’s eyes narrow in suspicion. ≈What? How—≈

≈I believe it’s my turn,≈ Shouta interrupts, and the young one’s teeth click together irritably. ≈What was the proposal you made that caused all of this?≈

≈That… we reclaim and rebuild the plateau’s reef.≈

Shouta frowns. ≈Trench sirens would be out of their element so close to the surface.≈

≈Yeah, obviously. That’s the point. I wasn’t suggesting it to the sirens.≈ He pauses, looking miserable. ≈It was to the corals and their kin.≈

Ice-cold distress shoots through Shouta’s veins, all at once. ≈Coral-fins,≈ he repeats slowly. ≈Living in deep-sea trenches?≈ 

Hitoshi shrugs. ≈Where else were they supposed to go? Your first siren must be a self-centered pufferfish type to have not mentioned them. Not surprising, though. Most treat corals and mixed-bloods like bottom-feeders.≈

The lower-caste are corals . Old guardians of the plateau’s ley-line, most slaughtered like farmed fish over a century ago. 

There are coral-fins living among the sirens.

Hizashi, he thinks, we finally found them. 

And hopefully it wouldn’t be too late.

≈...You still in there?≈ Hitoshi mutters, shaking Shouta from his shock. ≈I asked—≈

≈How many got away? How many are left?≈

Hitoshi’s eyelids droop, and in monotone, he mimics, ≈ ’I believe it’s my turn.’

Little shit. Shouta waves him on impatiently.

≈I asked where we are right now. Did… did I beach?≈

≈No. Your new walker friend found you with one of his devices; you’re on a ship.≈ But Hitoshi wears an expression of blank-faced unfamiliarity. What are they teaching the small ones down there? ≈A… walker-carrier that travels on the water. We’re still out at sea.≈ And, as it’s going to come to light one way or another, he adds, ≈Currently anchored over the plateau.≈

Lavender-on-black eyes widen, then the young siren responds like a lightning strike. ≈There’s two dozen pure corals left. Around a quarter that in mixed-bloods, though sometimes it’s hard to tell ‘til patterns come in.≈ Barely a pause. ≈Have— have the walkers found...≈

When he doesn’t finish the statement, Shouta takes a guess. ≈The heart of the ley-line?≈

Hitoshi’s ear-fins flare in confirmation.

≈They haven’t. Why?≈ 

And though it seems that the young guppy is trying to remain calm, Shouta can read him like a book; the fidgeting of excitement and worry and stress all clear. Try as he might to hide it, there’s hope in Hitoshi’s eyes.

It echoes the inexplicable hope that had surged through Shouta a month ago, when he insisted to Hizashi that they return to the plateau after all these years. It matches the thrumming in his veins, the whisper at the back of his mind, calling him to this graveyard of arcane energy he’d avoided for so long.

He pulls his hand away from where it had moved to rest over his heart.

Hitoshi watches him with a contemplative gaze. ≈You... feel it too, don’t you?≈

≈I don’t know why, or what it means ,≈ Shouta hisses back.

≈Isn’t it obvious?≈ There’s a crooning wistfulness to his voice now. ≈It’s almost ready. The ley-line is going to Sing with new magic again, after all this time.≈ He raises his gaze. ≈And I’m going to protect it.≈

In any other instance, Shouta might have laughed at such a bold claim, but the familiar conviction in Hitoshi’s voice leaves him without a slick retort. 

He is reminded of another, from long ago. A boy with a sky-blue body and pale, glittering fins; a cloud of white hair like an undersea flame; a blinding smile full of mischief and determination. You were always saying the same thing, he tells the memory. Didn’t I call you a fool, then?

Through the water and glass he hears the click of the door; Hizashi steps in, spots them, and offers a subdued smile. For a moment Shouta even sees him as they’d all met back then: a storkish blonde human, terribly loud, who could sing the stars from the sky without a pinch of magic to make it happen. 

Surely enough, his husband has a change of Shouta’s overclothes draped over one arm. Hizashi mouths, ‘Almost done?’

His chest aches with century-old nostalgia, but he nods and pushes off toward the wall by the stairs.

Hitoshi’s claws click against the glass behind him. ≈Wait, that’s it? You’re not going to tell me I can’t?≈

≈Why would I do that?≈

The question catches Hitoshi off guard. ≈B-because I’m mostly siren?≈

So the kid’s one of the mixed-bloods he’d mentioned, for all he doesn’t look anything like the light-colored reef-dwellers Shouta remembers. Figures. ≈I think that if the coral-fins’ numbers are as low as you claim, they’re going to need all the help they can get to keep the ley-line safe. Regardless of species.≈

He takes satisfaction in the surprised chirp the young one lets out, and almost, almost manages to grab the lip of the wall when he’s called for again.

≈H-hold on! Sosvii Aizawa.≈ The title of respect for adult mer catches Shouta by surprise; given the embarrassed darkening of the young siren’s face, it was probably accidental. ≈What’s going to happen to me?≈

Ah, there’s the question the moron should have asked first. 

≈You’re going to stay in here until you’re healed enough to swim and defend yourself. And you’re going to stop Singing at my husband and the other walkers while you’re at it. The trick you pulled earlier could have gone much worse.≈

Hitoshi’s face slackens. ≈Denki. Is he alright?≈

≈He says he’ll be fine, and I trust his judgment. But that’s not all.≈ He turns fully to face the siren. ≈I’m going to be clear with you, little fish. This setup is barely keeping you a secret as it is. And when walkers get injured in what should be a safe environment, questions get asked, and you’re ultimately only putting yourself in more danger of being found out.≈ He blinks slowly. ≈Not everyone on the ship would agree to let you go free.≈

Hitoshi slowly sinks to the floor on his side with wide eyes. ≈But you do?≈ he says quietly, almost like a plea. ≈And Denki? And him?≈ He gestures to Hizashi.

≈Yes. You can call him Yamada. We’re here to help you, Hitoshi.≈

The siren does not respond to that.

≈Get some sleep, guppy. If you need anything, ask me — but not where your friend can hear it.≈

Hitoshi’s ear-fins flare again, wordlessly.

So Shouta pulls himself from the tank, and mentally prepares for a day of hibernation in his sleeping bag, waiting for his slowly-forming gray-and-black patterning to once again fade away.


Chapter Text

Denki hobbles through his morning routine the next day with an extra dose of vigor, eager to go see Hitoshi as soon as possible. His plans are defeated, however, when he swings by the mechanical bay and a broken sonar component sits waiting for repairs on his desk.

He gives Bakugou a pleading look.

“Fuck no,” the other blonde grunts back. “While you played mother hen to an overgrown fish yesterday, I had to deal with some dumbfucks crashing a seafloor sweeper into a wall they ‘couldn’t see’. Prolly just too busy staring at a goddamn scribble on the ground to watch where they were steering. You’re getting off easy.” He jabs his thumb towards a messily-punctured sweeper. “That’s my project, you shit.”

His piercing glare says the rest; Bakugou had willingly took on the larger task.

Denki clasps his hands in a praying motion, murmurs, “You’re the best, man,” and promptly sits down to work.



Three hours later, he finally gets to the tank room. Yamada is trying to reassure Uraraka, who has donned a wetsuit and is wringing her hands nervously just inside the door.

“Yeah, there’s our golden boy!” Yamada practically shouts upon seeing him. “Great timing. Kaminari, how do you feel about being a peacekeeper today?”


“Professor Yamada says the siren trusts you,” Uraraka explains. “When I go too close to the tank he gets defensive. And after yesterday… well. Without Mr Aizawa here, it doesn’t feel like a smart idea. His only memory of me is also of being afraid.”

Denki blinks. “Where’s Mr Aizawa?”

Yamada claps a hand on his shoulder. “Staying in bed – not feeling quite himself today. But no reason to worry! I’ve already fetched your aquatic friend’s meals.”

“Hitoshi,” he murmurs back. At the pair’s confused looks, he shrugs. “His name is Hitoshi. Er. Sorta.”

Uraraka’s expression brightens in interest, but Yamada positively beams.

“Wow, Kaminari!” the former laughs. “You two really must be on good terms. He’s moving fairly well, but I need to change the bandage to make sure. Think you’ll be able to help?”

And that’s how he finds himself perched at the top of the stairs once again – albeit this time with more cushions to save his back and legs from further issues.

To his glee, Hitoshi doesn’t hesitate to swim right over, fingers curled over the lip of the tank. His hair droops over his face when he surfaces to his neck. The raised scales that speckle his cheekbones and forehead, ranging from lilac to dusky violet, glint under the light like embedded jewels. Denki wants to reach out and run his thumb across them.

“Hey buddy. Hitoshi.” He leans over his knees with a grin, which the siren subtly returns. Denki points to the bandaging on Hitoshi’s chest, over his lower right ribs. “How’s that holding up?”

Uraraka joins him then, kneeling at his side and giving Hitoshi a smile of her own. “Hello!” she chirps, unbothered by the mer sinking so only his appraising eyes and above remain surfaced. She puts her hand over her collarbone, as Denki had shown her. “Uraraka!”

Hitoshi’s ears flare, if briefly. Above water, they’re a dazzling mix of hues, even more spectacular with their translucent areas backlit.

“That means something like affirmation, from what I can tell,” Denki explains. “Okay Hitoshi, Uraraka—” he gestures to her to make the point extra clear, “—is the one who fixed you up.” He waves towards the bandaging. “She’s going to get in the tank… with you… and check your injury. Yes?” He charades what he can of the statement, Uraraka laughing under her breath with every movement.

But Hitoshi doesn’t acknowledge the statement with any sign of approval. Instead, one scale-spotted hand slides over the edge and comes to rest on the upper arch of Denki’s foot, clawed fingers and thumb settling feather-light against his ankle.

Denki’s mental track stalls, skips; He’s touching me. Sure, literally everyone else on the ship with knowledge of Hitoshi had beat Denki to the ‘physical contact’ milestone within an hour of saving the injured mer, but this is different, right? He reached out first, he wanted contact. He’s touching me.

Maybe he should be concerned that he can be tugged into the tank with minimal effort from this position, but damn. It’d almost be worth potentially drowning.

Unable to stop himself this time, Denki drops a hand and runs his fingertips across the back of Hitoshi’s knuckles, where his skin is decorated with sparse scales. His whole hand is eerily cold—which makes sense for a deep-sea dweller, he supposes—and almost fake-feeling because of it.

“Um, Kaminari?” Uraraka mumbles, interrupting the moment. Her cheeks are pink and Denki’s certain his are the same, if for completely different reasons that he doesn’t want to unpack just yet.

Right. He’s supposed to be getting her in the tank, not feeling up the hand of a pretty merman.

Hitoshi squeezes his ankle lightly, like a question.

“Ah… it can’t be me,” he tries to explain, wondering what kind of gesture he can give for this that won’t be taken as a rejection. He points back and forth between himself and the water, shaking his head. “I can’t go in the water, bud, I’m sorry. Tank’s too deep for me to get out, and these aren’t waterproof.” He taps a nail on the dark metal of his leg braces. “And I haven’t got the medical training she does, but… dunno how to act that one out…” he trails off.

Hitoshi’s eyes jump between the metal bands circling on either side of Denki’s knees, attached along the sides with sturdy rods and screws. His curiosity apparently wins over cautiousness because he rises out of the water enough to reach the lowest section of the brace, halfway up Denki’s calf. He slowly scrapes the deadly points of his claws across them, soft but deliberately, as if studying the material.

Denki stays stock-still as the reverberations from the act shiver through the metal and onto his leg. He’s traced the bands so many times on his own before, so it’s not an unfamiliar sensation. And somehow this is different enough to make his insides twist with anticipation.

But then Hitoshi sinks away and stares at Uraraka expectantly.

“Is... is it alright if I come in, then?” Her smile is still nervous.

This time, Hitoshi’s ears flare.

They spend a few minutes draining the tank down to a low setting again, Hitoshi looking more and more miserable as he rests along the bottom. With only five feet of water he’s forced to extend lengthwise to stay fully submerged. When they’d first put him in the tank yesterday, with levels this low, it hadn’t seemed quite this stuffy. Hitoshi being awake and clearly uncomfortable made all the difference.

Then Denki watches, with no small amount of envy, as Uraraka slips over the lip of the glass and plunges into the tank. Her hair billows momentarily before she finds her footing and stands.

Next to Hitoshi, she’s so small. Even though just yesterday Denki had stood beside the tank parallel to the siren, it hadn’t been enough to truly appreciate the size difference; Hitoshi rarely stretches out straight. Now, he floats near the surface on his back, chest and abdomen bared to the marine vet. He’s long and lean even before factoring in his tail, with thick deltoids and a pronounced collarbone. The drawn triangular build of his upper body looks straight out of a pro swimmer commercial, and jeez, why did Denki’s brain care about this now?

When Uraraka leans over the siren, fingers pulling gently at the edges of the bandaging, Denki catches Hitoshi’s gaze and immediately forces himself to turn his attention away. He feels his face flame and does not want to explain the reason for it, thanking whatever deities would listen for keeping Uraraka’s attention otherwise occupied.

The last thing he needs is for the others to know he’s attracted to a guy that’s half fish.

It’s not like he’s surprised, when it comes to the waist-up portion of his aquatic friend. In that regard, Hitoshi is very objectively good looking and anyone who would deny it, regardless of sexuality, is a total liar, he thinks. Even the siren’s face and its mythical features—horns, dark sclerae, scales—have an unconventional, foreign beauty to them that Denki finds himself entranced by.

His brain still isn’t sure what to make of the tail and the fact that Hitoshi is technically always naked, but hey, Denki shouldn’t be bashful on the other guy’s behalf.

And hell, he’d love to ask what the touching earlier had been all about. Is personal space usually so quick to disappear between merfolk, or is Hitoshi… acting out?


(It can’t be that, no, because give it a week or two and those wounds will be healed and the incredible, breathtaking siren will be out of his life forever.)

He’s dividing up Hitoshi’s food onto the swim board when Uraraka gasps. Denki checks back in on them in an instant.

“Is this normal for you…?” she asks in a wondrous voice, hands splayed on either side of the wounds. But they’re barely wounds anymore: just long, shallow gashes, dark as if bruised, indented as if someone had his scraped skin away with a bread knife.

Even Hitoshi at first appears mildly taken aback, but the expression rapidly fades into one of realization—and if Denki’s reading the sudden sharp grin right, excitement. Hitoshi twists his midsection experimentally but stops after a moment with a wince.

“You’re not entirely healed,” Uraraka tuts. The way she puts her palms on his chest to hold him steady hits Denki with yet another zap of jealousy, and he shuffles where he sits, working to keep it off his face. Uraraka pulls her hands away, oblivious, and continues. “Still, this is incredible progress. Your magical nature comes with some fairly nifty perks! You’ll be fully healed in no time – I can’t wait to check in tomorrow!”

Denki’s stomach sours further. In no time, huh?

Uraraka calls for the tank to refill, Yamada acknowledges with a shout of his own, and shortly the water level begins rising back up to full capacity.

Feeling like rocks have settled in his gut, Denki strips off his socks and shoes and hangs his feet over the edge. The chilliness of the sea makes him flinch when it reaches his toes, but he doesn’t pull back. Then the water laps around his heels, then up to his ankles. The valve shuts off partway up his calves—just below his braces.

He’s never been scared of water; he’d learned to swim just fine as a kid and was pretty decent up until the accident. Even then, trapped and broken and in the dark, the sound of the tides was all that kept him sane from the belief that he was never going to be found. The sea had saved him, hadn’t it?

He blinks the creeping memory away and flexes his toes in the salt water.

Next to him, Uraraka braces her hands on the wall and pulls her upper body out of the water with several strong kicks until she can maneuver to sit on the edge. Her cheeks are extra-rosy from the cold but she’s smiling, laughing to herself even, as she brushes her damp fringe aside. It’s only when she catches Denki’s expression that her own falters.

Oops, must not have been hiding those meddlesome emotions too well after all. He leans back on his palms with a sigh.

“Kaminari…” she starts, in the soft, pitying kind of tone that he hates.

But before she can say anything more, another pair of hands brace on the tank’s edge—one on either side of Denki’s spread knees—and there’s a surge of purple—

Hitoshi leans over him, propped up by strong, corded arms, and Denki forgets how to breathe.

The siren’s hair drips across Denki’s lap from how he’s angled into his space, and below the stairs his tail thumps against the tank wall to keep balance. His navel and hips are slotted between Denki’s knees, showing off the smooth transition from skin to scales.

And it’s a lot of skin, because he is right there, staring down from less than a foot away.

“Hi-Hitoshi,” Denki stammers in what’s nearly a whisper, caught frozen like a rabbit. His heartbeat’s so loud that it would be a miracle if the other couldn’t feel it somehow. “What—?”

Hitoshi must find his balance because he eases back a fraction, shaking his head to get his hair from his eyes. Once free from the weight of the water some strands curl up and others stand nearly on end, giving the mer an increasingly wild look, only helped along by the triumphant, challenging edge to his lilac gaze.

His chest is still though, Denki’s notes; he’s not using his lungs, and his vivid gills lay mostly-flat against the sides of his throat, filaments twitching as they try to steal oxygen from the air but fail. It’s got to be uncomfortable – why doesn’t he inhale? Has he never learned to do so before?

The siren seems almost expectant, borderline frustrated, but Denki cannot for the life of him figure out why.

Uraraka scoots backwards with a grin, fiddling to work down the zippers of her wetsuit. When Denki looks over she practically coos at him. “Isn’t that sweet, Kaminari? You won’t go down to him, so he came up to you!”

But it appears to be a bit of a struggle for him; between his inability to breathe and the way he winces—right, that injury hasn’t gone away—Hitoshi probably can’t last holding himself up like this for too long.

Denki slowly straightens, aware that now he’s the one crowding space, but the siren doesn’t seem bothered in the slightest. In fact, when Denki awkwardly holds his hands between them (what is he supposed to be doing? What’s being asked of him??), Hitoshi’s aural fins flick forward then fan out wide. The display brings to attention the numerous subtle differences in color within, like a beautiful abstract painting, or a bouquet of flowers.   

Despite the cold water dripping across him and the chilly arms framing his legs, Denki suddenly feels unbearably warm.

A laugh bubbles up from inside of him, genuine and bright, and before he can stop himself he’s lifted his hands to those fins. “Show-off,” he murmurs with a smile. He gently drags the pads of his thumbs across the webbing, feeling it twitch under his touch, even as Hitoshi keeps his face still. It’s thin and rubbery, translucent near the outer edge and brilliantly speckled with a dozen hues of purple towards the skin. Further up, the fin has a stiffer build, the way it overlaps on itself almost featherlike. Denki brushes his fingers over those sections, fascinated.

And if he hadn’t been so close, he might have missed it: a strange low trill that pulls from deep in Hitoshi’s throat. It’s brief, a few seconds at most, before Hitoshi jerks back an inch with wide eyes. The siren blinks, lets out a choked-sounding chirp—then he’s shoving off the wall and surges back into the tank with a splash that soaks Denki to the bone.

“Okay then,” Denki sighs as Uraraka howls with laughter.

Even when Denki ‘serves’ the food onto the kickboard and places it on the water, Hitoshi doesn’t come back up again, for whatever reason adamantly submerged on the opposite side of the tank.

Yamada is smirking when the two of them finish descending the stairs. “We’re gonna get you in the water next time, Kaminari!” he jokes. “Poor Hitoshi looked about ready to beach himself to please you, didn’t he?”

Denki’s ears go pink yet again. “I-I don’t even know what he wanted - and I think I upset him.”

That makes Yamada falter. “What makes you think that?”

“He made this… sound?” Denki shrugs. “I don’t really know how to explain it, Professor. Like a low buzz and— what?”

But the man spins away, hand over his mouth, stalking towards the tank. Denki can’t see his expression but he does see Hitoshi, who reacts to Yamada with flat ear-fins and a scowl.

“Say, Kaminari. You have overcoat canisters for the rovers and other devices down in your work bay, don’t you?”

“Er, yes?”

Yamada turns, grinning. “Any vapor barrier types among them?”

“Yeah, of course.” Those are arguably the most important; salt water’s quick to eat through metal that spends a lot of time submerged in it. The vapor barrier coatings help devices keep their integrity—

Oh. Duh.

The professor props his hands on his hips. “So, if I were to ensure you’re safely able to get in and out of the water, and move around within it when necessary, would you be up to taking the plunge?”

Yes,” Denki breathes as quickly as his mind can parse the question. “Of course, I don’t know how I didn’t even consider before—it’ll take a few coats, so many little parts I’ll have to do separately and put back together but— but yes, yes I definitely— I could probably be done for tomorrow—”

“Then let’s plan for that!” The bright man looks like Christmas has come early; why he’s excited for the prospect, Denki can’t imagine.

So he falters. “But, sir. Why...? I can’t offer any skills to help him...”

“Kaminari. You want to spend time with Hitoshi, don’t you?”

Is that even a question? “Y-yes.”

“And he wants to spend time with you?”

He thinks to yesterday, when the siren had accidentally tripped him just to stop him from leaving, and all of the little touches and actions today that seemed to have the sole purpose of bringing them together. “I… think so?”

Yamada nods. “Lastly, what do you think the objective advantages of a close bond with him might be, once he’s released?”

Denki thinks harder on that one. He remembers Bakugou bringing up a reason for earning Hitoshi’s trust - so that the researchers could keep some sort of connection to the mer and not lose them for another century or so. To find out why they’ve been staying away.

But he also doesn’t think that’s the only answer.

“He doesn’t have anywhere else to go,” Denki mumbles at last. “If he trusts me, then… maybe he’ll let me help him. I don’t know how but — I feel like he knows he’ll need it.”

He’s important to me, he doesn’t say. And I want to be important to him.

Yamada looks pleased. “That’s as good an answer as any, listener! And with that settled, I’ll make sure we have the means to get you navigating the water in short order!” he winks.

With renewed excitement, Denki hobbles to the tank, tapping until he has Hitoshi’s attention. The siren looks hesitant to even glance in his direction at first, still half-scowling, his face-speckles seeming more vivid somehow— but he does finally meet Denki’s stare.

“Tomorrow, Hitoshi,” Denki promises, getting a confused fin-flick in response. “Tomorrow.

He does the first coating before bed, but stays up late into the night, remembering their closeness with a lightness in his chest.

Chapter Text

The expeditioners who keep breaking their equipment must be conspiring against him, judging by how efficiently they keep him supplied with small tasks the following morning. Bakugou’s on his day off, so Denki’s left to handle it all. It’s a stroke of luck that he’d gotten the second coating done on his braces before the workload piled on. When he’s finally able to escape the workbay it’s well past noon.

He’s taken aback to find the full count of secret-keepers gathered around the table in the tank room. Unease settles in his gut, but a quick glance to the tank itself assures him that Hitoshi is alive and well. 

“Took your goddamn time,” Bakugou grunts.

Normally he might meet that with a quip of his own, but right now the mood in the room is too distracting that the only words he can bring forward are, “What’s... going on?”

For a moment nobody seems quite sure how to answer that; Denki looks from Aizawa, who has a heavily-bandaged neck, to Uraraka, half-out of a sopping wetsuit, and finally to Yamada. The lanky blonde grins but it doesn’t quite reach his eyes.

“Well! There’s some good news, some bad, and some… perhaps a tad borderline. Subjective to opinion. Which would you like first?”

The agitation inside Denki grows, unfurling like cold tendrils through his limbs. He swallows. “Let’s start with the worst and rise from there.”

Yamada waves him over to a seat, between himself and Aizawa. Denki sits stiffly.

“So,” the professor starts with a short sigh. It’s unnerving to see him so muted. “When all of this happened, we never properly booked this tank for our use. And without a good reason for why a historian would need such a thing, I didn’t do that after the fact, either.” He drums the fingers of one hand against the back of the other. “A request for access was placed this morning by the biology team - we can’t contest that. Even the lock change went under the radar. If we push back, it will only raise suspicions.”

Denki’s mouth is dry. “Okay,” he says, swallowing. Then, logically—

“Which brings us to the middling news.” There’s that smile again, with traces of a grimace. “I was able to hold them until tomorrow morning, citing a need for time to get my research papers and exhibits organized! We’ve still got the rest of the day, little listener. Nobody outside this group is any the wiser about Hitoshi, but…” He must see Denki’s realization written on his face, voice faltering and forced smile receding. It turns apologetic.

“We’re releasing him tonight,” Aizawa finishes gruffly.


Denki slowly leans back in his chair.

Tonight. That’s it, then. 

Just yesterday he’d been counting down in terms of weeks, not knowing for sure, but definitely not expecting the siren’s wounds to close up literally overnight. Surely Professor Yamada or Aizawa would have known something more about this rapid healing? They are the experts. They could have said something. Could have stopped him from—

From what?  His devil’s advocate bites back. From getting attached? That’s all on you, dunce.  

“The good news is that he’s all healed up,” Uraraka offers helpfully. “From what I can tell, that is. We won’t know for sure until he’s got a stretch of open water to work with. Still, even if it means swimming against a current, he should have no issue getting home!”

She doesn’t know?  Denki catches Aizawa’s eye; the man gives a subtle shake of his head, a warning. So the other two hadn’t been informed of Hitoshi’s predicament. 

“That’s… good to hear,” he says, but his voice sounds dull and unenthused even to him.

“Tch.” Bakugou gets to his feet, storming off towards the tank as if it had personally offended him. “You’re s’posed to get dunked today, aren’t you? Hurry up and get over here then.”

Denki looks up sharply, then glances at Yamada. “It’s still alright—?”

The man’s got encouragement written across his face, even if it’s less animated than the day prior. He settles a hand on Denki’s shoulder and gives it a squeeze. “I think it’s the best idea in the world, right now, listener. For you and him both.” He seems like he wants to say more, but doesn’t.

Denki doesn’t need to be told twice. He lets Uraraka link her arm with his and pull him towards the tank.

He doesn’t have a wetsuit of his own—there’s never been a need, and the full ones are very pricey—but someone has managed to find an upper-body piece in his size to keep his core insulated from the chill of the seawater. Which is fine with him, because he’d already put on swim trunks under his leg braces and there’s zero chance that he’s going to take either of those off in public, thank you very much. It’s bad enough that he has to go topless for even a short while in front of his peers and Hitoshi, all of which (save maybe Yamada) are much more physically built than he is.

And if he’s left pink-faced by the siren’s gaze—intent and never straying as Denki strips off his t-shirt—well, that’s another thing entirely. Uraraka is kind enough to only giggle when Denki fumbles the arms of the wetsuit top, and at last she zips up the back of it without a word. It’s perfectly snug, and the sleek lifejacket he’s handed next fits overtop.

He’d hoped that the silence would extend to Bakugou as well, but maybe that was too much to ask.

“It’s only been two days, you dumbshit,” his explosive coworker snaps, adjusting the chains on the hammock-like seat that’s meant to raise and lower Denki from the water. “Two fucking days, and you’re pining like a goddamn teenager. Over a fish.

How’s he meant to respond to that? Denki reasons that if the other blonde noticed then it’s a sure bet everyone else has caught on as well. Besides, Bakugou’s not wrong. He swallows. “Aah, well. Yeahhh.” Nice reply there, brain. Thanks for that. “It’s stupid.”

“Damn right it’s stupid.” Bakugou’s checking over the pulley system almost aggressively. “Why’d you let yourself get all twisted up? You knew it’d end with sending him back. Did you fucking expect another outcome?” He then mutters ‘and he’s a fish,’ a bit quieter, still in disbelief over that fact in particular, Denki supposes.

Denki struggles to find words to describe the roiling discomfort in his chest. “....No,” he admits. “Couldn’t help it. I just like spending time with him.” A ball of tightness forms in his throat, and try as he might, he can’t choke the words back. “Tonight’s gonna suck.”

Bakugou huffs, turning his glare on Denki for a long moment as if disgusted even just by the implication of feelings. Then he shakes his head. “For fucks’ sake, Creaky.” He motions to the seat. “Whatever. Get on and go float with your shitty asshole fish crush.”

That has Denki’s heart leaping nervously again—but he obliges as Aizawa joins Bakugou at the makeshift pulley and they bicker quietly over something he doesn’t listen to. Instead, he turns his attention to the tank again.

Hitoshi has surfaced to just above his nose again, staring up unblinkingly. The gentle ripples in the water are distorting the rest of his face, hiding his expression.

Does he know? Had the others found a way to tell him about his impending freedom? The siren’s visible elation the day before about his own healing progress suggested eagerness about getting back to the sea. Surely now Hitoshi must be wondering what they’re going to do with him next; he can’t fault the guy some trepidation. 

Maybe that’s why he’s back to watching Denki like he’s unsure. Hesitating to come close. Or maybe, unlike Denki, the siren was content to be distant now that his freedom was a few short hours away. Please don’t let that be the case.

“So bud,” he says amiably, getting settled. “You’re not gonna try and drown me for real this time, are ya? We’re past that, right?”

It earns a snort from Bakugou, at least.

Then something’s tugged over his hair; goggles? Aizawa sighs from right behind him. “Having second thoughts? Nobody’s making you do this.”

“No,” Denki replies instantly. “I— I really want to. Just… nervous.”

“Just keep your fingers out of his mouth and leave his gills alone. Don’t touch the upper thoracic fin, either—the one below his neck. Try not to bleed. Avoid all that, and he shouldn’t bite.”

“I meant nervous about the water…

He hears a chuckle from Yamada down on the floor, and Aizawa grunts. “Hm. Don’t be. We’ll keep an eye on you. Both of you.” The latter is clearly aimed at Hitoshi, and the siren’s ear-fins settle back as if he’d somehow understood.

A minute later, the seat swings out over the water, and Denki is eased down into the tank.

By the time the freezing water is up around his waist, his heart is thundering a thousand beats per minute. Part of it is no doubt the feeling of being trapped, unable to get out of here on his own (—is this what Hitoshi’s been faced with for days? Gods). Another part is because he’s blatantly aware of the long purple tail and fins curling beneath him like a shadow, and the lilac-on-black eyes that haven’t left his face.

Then he’s dropped further, and finds himself stabilized only by the lifevest.

For a moment, when the seat disappears, he flounders. Childhood instincts tell him to kick, kick to tread but he knows if he does it’ll hurt like a bitch. He flails instead, cupping at the water and trying to compensate for the awkward way the lifevest tries to force him onto his back.

Webbed fingers tangle in the vest’s front straps and pull him upright again. 

Wide-eyed, Denki reaches forward instinctively—he grasps onto smooth, cold forearms and sucks in a breath. And just like that, he’s stable. The flash of alarm subsides almost immediately, giving way to relief, and he grins so wide his cheeks hurt at the sight of the siren keeping him balanced. “Hey there, Hitoshi.”

Hitoshi’s aural fins spread wide, his eyes narrowing softly. When he lifts his chin above the water there’s a warm grin curving his dark lips, too. His shark-like teeth flash for a moment. “Denki,” he chirps, low and quiet, just between them.

Whoa boy. Denki inhales shakily, willing his pulse to steady. He slides his hands from Hitoshi’s forearms to his elbows, feeling the skin give way to pebbled scales, and then to timidly settle at the base of the siren’s biceps.

“This is wild, huh? I don’t even remember the last time I went swimming. It’s been years. I was pretty good back then! Maybe not as fast as you, I bet you’re real damn speedy when you get out in the open water.” Then he swallows. In the back of his brain he’s aware that they’re being spectated, so he can’t say too much. Can’t say exactly what’s on his mind. He lowers his voice to a murmur instead. “Hope I’ll get to see that.” His chest aches.

Hitoshi slowly releases the front of the lifevest, giving time for Denki to find his balance. Then the mer sinks beneath the surface. Right, gills. He doesn’t immediately come back up, however, circling below languidly and curiously. Denki feels the tap and scratch of thick nails against the brace-bands on his thighs, then a silken fin drag across the sensitive bottoms of his feet, making him flinch. Just out of his sight thanks to the obnoxious vest, Hitoshi wraps a hand around his ankle, curling and prodding inquisitively.

Don’t pull, please don’t pull, he thinks, still working hard to stay balanced and upright.

Thankfully Hitoshi moves on, sliding his fingers up one calf, brushing over a knee. The siren’s other hand cups the back of it and gently encourages it to bend, testing the unfamiliar joint and bones with near-reverent care. 

Meanwhile, Denki is having an internal crisis, face aflame despite the cold. The mer’s probably clueless to just how intimate the actions are, right? When Hitoshi’s thumb sweeps thoughtlessly over the sensitive inside of Denki’s thigh, it’s all he can do to not jerk and topple onto his back with a squeak. 

Over the sound of the filter, he hears Yamada call out, “Might be a good time to set some boundaries, Kaminari!”

Still being watched. Yup. A glance to the side tells him Bakugou and Uraraka have left, but that doesn’t mean he’s gung-ho for where this is going.

He dives a hand down, finding a billowing mess of hair; his knuckles knock none too gently against a dull-tipped horn. It’s enough to make the hands on his legs pause, then release, as Hitoshi drifts back to the surface, silently questioning.

“Congratulations,” Denki breathes out, hoping he doesn’t sound too flustered. “You’ve discovered legs! Fantastic things, when they work right, but— ah, wh-what now?”

Hitoshi is circling again, but this time near the top of the water where Denki can see. The siren lazily meanders behind him, then around to his other side, fantastically long tail trailing his upper half. Soon Denki’s surrounded by a full loop of dusky-lavender skin and amethyst scales.

And his fins, hell. Denki may have gotten very familiar with the siren’s ear-fins yesterday, but they’re small compared to the soft, sweeping sheets of vibrant color flowing from Hitoshi’s back, sides, and tail. He’s terrified of touching them the wrong way— what had Aizawa said to avoid? The one near his neck? Did that mean the others were fair game, or…?

Hitoshi murmurs something in his odd language, and to Denki the inflection almost sounds irritated—but the siren’s smirking at him. Another statement follows it, shorter, then after a moment of silence when Denki shrugs hopelessly, Hitoshi flicks his ears and takes one of Denki’s hands, settling it firmly over the glittering expanse of scales near the end of his tail.

“O-oh,” Denki peeps. He lets out a shaky little laugh. “Alright, okay.” That answered his previous question, he supposes.

Beneath his palm, the scales are sleek—at least in the area he starts carefully stroking across. But when he curls his other hand to the opposite side, what he assumes to be the rear of the tail, his skin catches on infrequent ridges and raised edges. 

“These ones are spiny,” he says, surprised. They remind him a bit of coarse sandpaper when he runs across them backwards. The pad of his ring finger cuts on one of the scale-teeth and he gasps at the sting. “Shit, should have expected that.” He shakes his hand in the water with a grimace. “You’re really built like a weapon, arentcha?”

But Hitoshi is suddenly tense, staring at Denki’s fingers. His eyes are strange too, like the colors have shrunk small and left more of the void in their place. And he’s so still , unblinking, only his nostrils flaring gently.

“Kaminari, are you bleeding?”

He whips his head around; Yamada and Aizawa are standing at the glass, the latter with one hand on the stair railing and ready to climb.

Oh, fuck.

Without answering he jabs his injured finger into his own mouth, frightfully aware of Hitoshi’s pin-pricked gaze following it keenly. He tastes mostly saltwater, but there’s copper to it, too. 

The siren grabs his hand and tugs, pulling the finger back out. Before Denki can stop him, Hitoshi presses the pad right below the cut—it’s so shallow, barely there—and watches a small bead of red gather at the end.

Shit shit shit. Denki yanks back, but the siren’s grip doesn’t falter. “Stop— p-please—” What had Aizawa said? No teeth, no gills, no neck fin, no bleeding. He’d managed to bungle the last one already and now his hand was getting far too close to the first for comfort. “Hitoshi, please—

Something bright and yellow knocks the siren’s head aside with an audible, foamy thud before dropping to float on the water. The kickboard?

He doesn’t have time to ponder it; a deep, guttural growl rumbles out of the incensed mer in front of him, chilling Denki to the bone. Hitoshi’s face is pulled into a terrible snarl, all teeth on display, but he’s looking upwards and over Denki's shoulder.

“Snap out of it!” comes the roar from above, and shit, Aizawa’s got a pair of lungs on him.

Denki’s wrist clicks from Hitoshi’s iron grip, the blood on his poor finger tracking down into a thin line. Thankfully the siren is otherwise distracted, thundering out some incomprehensible remark with hisses and rumbles and clicks. Denki wants to do something, anything to calm the situation down, but his only remaining workable limb is having to compensate for being tugged completely off balance.

Aizawa shouts something else but it’s lost in noise as Hitoshi ducks to avoid another thrown object. Despite the lifevest, Denki is briefly tugged under as well, and comes up spitting salt. 

“Hitoshi,” he tries again, coughing. He finds himself held closer to the siren, which is great for balance but also sucks because it’s like being up against a revving chainsaw. “Mr Aizawa, sorry but you’re just making it worse—”

Breathing heavily, he glances at Yamada through the glass; the man is surprisingly silent. When their gazes meet, something uncertain and apprehensive pulls across the professor’s features.  

Soundlessly, desperately, Denki mouths ‘what?’

Yamada’s eyes flick up to his husband and back, then to Hitoshi, as if indecisive. He closes his eyes for a moment. When he opens them again, a certain degree of confidence is back. He gestures to Denki, taps his forehead, points to Hitoshi, and taps his forehead again.

Alright. Okay. Get even closer to those teeth? Can do, he supposes. Hopefully he’s not misunderstanding the suggestion. Steeling himself, Denki dips further into the water, and gets a better grip on the siren’s shoulder.

Then using the momentum of coming back up and all of the strength he can manage, he lunges up and gets his free arm hooked around the back of Hitoshi’s neck. Denki closes his eyes at the teeth so frighteningly close to his nose, tenses at the snarl, and drags Hitoshi down enough to press their foreheads together.

The noise softens and peters out in a matter of seconds.

“Ohh… oh gods, aha, Shou, don’t give me that look, i-it worked,” Denki hears Yamada warble weakly— and promptly turns his attention away from that.

Because when he opens his eyes, Hitoshi’s own are right there, wide and bright and shell-shocked. Denki pulls back cautiously, waiting to see if metaphorically taking his finger off the magic button is going to revert this peaceful, much appreciated change— but it doesn’t. He lets a relieved grin take over his expression, relaxing against the mer’s torso, out of breath.

Hitoshi’s aural fins slowly spread to their full height and width, and if Denki wasn’t still a bit dizzy from the whole affair he might say that some of the scales on the siren’s cheeks were faintly glowing.

“Time to get out, kid,” Aizawa grumbles loudly.

But Denki pays him no mind, doubly so when Hitoshi’s hold on his wrist loosens considerably, and the mer’s other hand tentatively comes to rest on his hip instead. There’s a moment of tension all around when the bleeding finger is called back into attention, but Denki wills himself not to panic this time as Hitoshi brings it to his mouth.

The siren’s dark tongue slowly skirts over the line of red, leaving a tingling sensation. Denki can feel a shudder ripple through the body he’s pressed against, and holds his breath. But no bite comes; in fact, Hitoshi almost looks nervous himself as he studies the tiny injury. And then he releases the hand entirely.

Denki looks at his finger, perplexed, dabbing the pad with his thumb. The tiny cut’s still there, but coated thinly with a clear layer that’s stopping the bleeding.

“N-noted,” he mumbles, pink and mentally reeling. “Thank you. And I’m— I’m sorry, Hitoshi, I shouldn’t have freaked out. I trust you, I do, or else I wouldn’t have gotten in here, but I guess I thought the warning was real a-and—”

He’s silenced by Hitoshi’s forehead butting gently against his again, and. Hm. Yeah, that’s its own strange but totally valid method of pacifying, isn’t it? He lets go his breath, closes his eyes. Who cares how this looks? Not him. Not right now.

Aizawa clears his throat.

Without missing a beat, Denki smiles. “Nah, sir. I think I’m good right here for now.”



Shouta collapses back into his chair with a grunt, eyes narrowing at his husband.

“I’m not sorry,” Hizashi murmurs, but it’s not convincing. 

He’d been plenty sorry the instant they’d both recognized the single-focus in Hitoshi’s eyes; friends or not, the guppy’s still a bit of a wildcard and Aizawa remembers plenty of young sirens who weren’t able to shake the predator instinct once triggered. Maybe it’s because the little fish is a halfbreed that it worked.

Or, he concedes irritably, Hizashi was right for once.

“Kaminari cares, Shouta. It’s fast and new and probably terrifying, for both of them. You remember what that was like, don’t you?” His husband smiles brightly, if a bit sad in the eyes. There’s so many bad memories intertwined with the good that it’s impossible not to feel everything all at once when they recall those days. “Earlier, when we told him—gods, the look on his face. It was just like…” He shakes his head as words fail to come.

Shouta reaches across the space between them and entangles his scarred fingers with Hizashi’s slender ones. “So he cares,” he admits quietly, watching the pair in the tank cling to each other as the human kid in question rambles on about who-knows-what in an airy voice. “That doesn’t mean he has to know. Or get involved.”

“He’s already involved. When Hitoshi comes back for him—”

If .”

Hizashi pauses, then laughs. “Shou darling, I recognize a lovestruck siren when I see one. But fine. If Hitoshi comes back for the boy… I’m going to help them. Tell them what they need to know to be ready, to make it work. But I don’t want to do it without your permission.” Then his husband’s clear green gaze falls on him, hopeful. “Please?”

Shouta sighs deeply, rubbing idly at the edge of the bandages around his throat that cover his gills. The whole mess with the ley-line is going to be a pain even without the budding feelings between two lifestyle-incompatible problem children. But it’s the same sire-like gut reaction as before telling him that; he can’t very well tell the little fish how to feel. He’d be a hypocrite of the first degree. 

“Fine,” he murmurs under his breath, squeezing his husband’s hand gently. “If you think it’ll help protect them from everything else that’s coming, let’s do it.”

He can feel Hizashi’s giddiness without looking, the warmth blossoming through his other half at the response. But it’s nothing compared to the overwhelming tidal pull of reassurance that sweeps through him when Hizashi pulls their heads together. Briefly, softly.

Yeah, he thinks, let’s keep them safe this time.

Chapter Text

It takes a good deal of Hizashi’s convincing to get Kaminari out of the tank for good, after a few hours of exhausting in-and-out to give his body the breaks it needed. The last time Shouta pulled him up, the kid’s face was already pinching in that sad way that would no doubt set the tone for the rest of the night.

Even more monumental of a task is getting him to leave for a little while so Shouta can speak to Hitoshi, and communicate what’s going on. The kid’s determination to spend every remaining moment with the siren is a pain in the ass, but on some level, he understands.

That still doesn’t stop Shouta from secretly cranking down the temperature in the room until Kaminari’s teeth are chattering and he agrees to change out of his wet clothes.

“It was the logical option to prevent suspicion,” he says dryly to his husband, who’s also shivering and scowling now that the boy has zipped away. “Keep an eye on the hall?”

When Hizashi scoots out the door, looking pleased to escape the makeshift fridge, Shouta allows himself a smirk. He turns the temperature back to a reasonable level before making his way over to the tank.

Hitoshi wears a dazed, fond smile, which only fades a fraction as he floats down to Shouta’s level. His fins are all still half-flared in contentment. Every line of his body is relaxed and nonchalant, as if Kaminari had been a strong drink, leaving the siren calmer than Shouta has ever seen him. But he knows it won’t be long lasting.

Shouta clears his throat. Vocalizing Mermish sounds above water is an extraordinarily difficult task, complicating further when relying on lungs.

≈We’re letting you go now.≈ Best to keep it blunt. ≈Some of the other walkers on the ship want to use this tank, and we need to get you out before they come looking.≈

Hitoshi stills, the lazy smile slipping as he processes. Then his expression flits between so many others in such rapid succession that it’s hard to keep track. Surprise, relief, excitement—and then it lands on hesitation, ears slowly folding back against his hair. ≈Makes sense,≈ he murmurs back, casting his gaze down and aside thoughtfully. ≈I feel really good. No pain left at all. Guess the ley-line being so close by gave me a boost.≈

≈Mm. You’re going to look for the heart of it, I presume?≈ Of course he was, if his resolve hadn’t dissolved under the human kid’s reverent touches. He watched the siren’s aurals flare in confirmation. ≈Then be careful. Other walkers from this ship are prowling down there with their devices. They got close enough to hit the guardian’s aura barrier yesterday; the sonar didn’t pick it up, obviously. So now they’re asking more questions. If you’re seen, half the rasyakiin he uses the word for magic-leechers, those that hunt the ley-lines and steal their power — ≈ stalking the Pacific will be out here within a day, and our goal of protecting it will be hopeless.≈


≈Yes,≈ he mutters, crossing his arms. ≈Yamada and I have a combined interest in keeping it safe, and we’re going to help however we can. We want to be here for you. You can rely on us, Hitoshi.≈

Shouta wonders, as the young siren looks at him in bafflement and awkwardly rubs an arm, if nobody has ever said such a thing to him before. There’s a bare hint of coral-like glowing on his cheeks—likely unnoticeable to someone who didn’t know to look for it—and he opens and closes his mouth subtly a few times, lacking a response.

≈Just to be clear,≈ Shouta starts again. ≈The offer isn’t intended to make you uncomfortable or to suggest we should take the place of your pod back home

≈I don’t have one,≈ Hitoshi blurts out suddenly, then immediately looks as if he regrets that.

Ah. Hmm.

Now Shouta’s the one struggling for a comeback. He’s angry, not at the youth in front of him but at the implication that the deep-sea dwellers have failed to support one their own yet again. This time, what for? Because one of his parents wasn’t trench-born? Even they had left him unbound, podless.

No wonder Hitoshi’s affection for the human kid had developed so fast, if attention and kindness had been in such short supply before.

Before Shouta can formulate a sensitive reply, the siren speaks up again, expression guarded. ≈Is… Denki part of your pod?≈

He huffs in amusement. ≈Guppy, I doubt he even knows what a pod is. Most walkers don’t understand much about merfolk.≈

Hitoshi ponders that for a moment. ≈But you look out for him. You protected him when—when I—when he was hurt.≈ The grimace prefacing his wording change is a subtle kind of alarming; if the young siren’s already feeling the instinctual, sharp mental pressures to safeguard loved ones, then he’s fallen even harder than Shouta thought.

≈I do, and I did,≈ he agrees. ≈As I explained before, when the walkers are harmed, it causes problems.≈ And if there’s more to it than that, like maybe that the kid really is growing on him (much to Shouta’s resignation and Hizashi’s glee), then he’s certainly not going to admit it out loud. Besides, he has a feeling he knows where this line of questioning is going, and puts on his sire mind again for a moment. ≈What is it you’re expecting from your relationship with him, Hitoshi?≈

The siren’s fins flatten defensively, nervously. ≈Why do you care, if he’s not in your

≈Relax,≈ he interrupts, not wanting to deal with unnecessary posturing. Already Shouta can feel his throat ache as he represses a calming trill. ≈It doesn’t make a difference to me. However. ≈ He glances back at the door briefly. ≈I’m more experienced when it comes to walkers. Your friendship with him is risky, but not impossible to maintain. And yet I believe you’re starting to wonder if he could be more than that.≈

Hitoshi stays quiet and motionless, which is confirmation enough.

≈I’m not here to judge, little fish, but I’ll lay some facts out for you. Your friend can’t swim, can barely float. His legs aren’t going to heal like your injuries did. Not ever. He’ll be land-bound, and even if you learn to use your lungs, you’ll never stray far from the shore as you are now.≈ He pauses, watching the melancholy steal over Hitoshi’s gaze as the siren glances away. ≈He’s a great kid. Surprisingly so, the rare kind that are few and far between. But great enough to give up the ocean for?≈

Hitoshi’s eyes snap back to him. ≈Give it up? For… good?≈

≈It’s a trade-off. Can’t have it both ways, guppy. When you give up your fins to live on land, you’re cutting ties with the sea. You’ll lose most of your magic. There won’t be enough to turn back if you change your mind. So, decide if the kid is worth that.≈

Shouta averts his gaze. It’s painful to watch Hitoshi drift to the tank floor so quietly, eyes rounded with shock. Shit, he’s such a young thing, and he’s got enough to worry about without having to consider finding a mate. Maybe Shouta should have worded that differently, should have insisted that he didn’t have to decide now. But with the speed those two are going, perhaps this is for the best.  

He’s beginning to think their conversation has ended, when Hitoshi asks something Shouta probably should have expected at this point, all things considered.

Sosvii Aizawa  was Yamada worth it, for you?≈

When he closes his eyes, he hears the wordless whispering of magic, dim and soft, a reminder of what he gave up. With the ley-line growing stronger his memories have become clearer, and sometimes it even feels like his Song might work again, dare he use it. But he doesn’t. He knows the whispers are just echoes.

Shouta turns back to the younger siren, one hand sliding behind his neck to rub at the prominent C7 bump where a thoracic fin once began. ≈He was. Still is; I don’t regret my choice. But the sea calls and calls, and never stops, Hitoshi. And without its magic… it’s difficult to protect what’s important.≈

Behind him, he hears Hizashi open the door, and in the reflection of the tank he sees his husband— his mate, his most precious, his to take care of— step back in, followed by an anxious Kaminari.

≈So,≈ he murmurs, as quiet as he can manage. ≈Do you think you could give that up to be with him?≈

Hitoshi stares past, silent as a grave, looking utterly lost.



It’s not that Denki has anything against Professor Yamada—not in the slightest—but seeing him standing outside the tank room’s door, clearly waiting to talk, sours his already-finicky mental state.

“Kaminari! You’re back.” The loud statement strikes him as a bit odd; it’s not like there’s anyone else around to announce it to. Yamada leans down a fraction and lowers his voice. “How ya doing, kiddo?”

Gods, what a question. Over the last half-hour he’s faced emotional whiplash of the worst kind. The moment he left the tank, his dopamine ran dry as he realized that this was it.

The pit in his stomach is growing by the minute. “Bakugou says I shouldn’t have gotten attached. I didn’t mean to, but I…” It hurts, and it’s going to get even worse. But his worry isn’t for him. “Professor Yamada… if Hitoshi can’t go home, what’s he going to do? C-can sirens survive on their own?  He’s going to be lonely.”

Denki knows a thing or two about loneliness, but he’s not exiled and one of the last of his kind.

Yamada gives him a sad look. “You don’t seem very confident that he’ll come back, kiddo.”

“I just don’t see why he would. I’m… me.” He can feel himself tip-toeing to the edge of hopelessness. “I-I’ve had fun. Really, these last few days have been surreal, and I don’t think anything will ever compare. S-so… I should just be grateful that I got this much.” Denki looks at the door. “Does he know he’s going free?”

Yamada nods and steps inside.

The tightness in Denki’s throat threatens to choke him. He ducks his head and pushes through the door after the researcher, then takes a deep, shaky breath, finally ambling over to where Hitoshi waits.

“Hey buddy,” he murmurs, willing his voice to steady. “Bet you’re looking f-forward to stretching your fins, huh? A-and no more privacy invasions at all hours of the day. You haven’t gotten too attached to my five-star food service, have you?”

The absent, destroyed look in the siren’s gaze as it falls on him nearly breaks Denki to pieces right then and there. It affirms his fears, doesn’t it? His chest clenches painfully.

When the tears start falling he tries to wipe them away. “Sorry, s-sorry… y-you’re hella strong. You’ll be fine.” He hiccups, forcing a smile despite his voice breaking. “I will be too, just... y’know. I’m gonna miss our little chats.” He gives a hysteric half-laugh.

Hitoshi’s face turns concerned, and Denki can’t blame him. The language barrier has never felt so insurmountable as it does this very moment.

He’d seen Aizawa standing near when he’d approached the tank, but it still makes Denki jump in surprise when the man starts talking softly. “Your veterinarian and technician friends are on their way. Once they arrive, we need to move fast, and get him off the ship before security personally looks into why we’re opening the docking pool so late.”

The words themselves may be clinical, unfeeling, but Denki understands the meaning behind them: Say your goodbyes now. As if to punctuate it, Aizawa squeezes his shoulder and gives them privacy.

Denki’s throat tightens further—no , stop, he still has so much to say! He doesn’t want them to part with this misery having stolen his last words. As he struggles to catch a breath, he sees Hitoshi rest his head and palms on the glass, eyes closed. Denki’s tears spill ceaselessly as he mirrors it, still fighting to keep a smile that feels like it’s fracturing.

“A-am I allowed to ask something selfish? It’s okay because you don’t understand me, right?” he whispers hoarsely against the glass. He inhales deeply again. “It’s just… I don’t want this to be it. You make me feel like I’m a part of something special. Not just a shadow anymore, y’know? Maybe it’s hopeless, to want this to continue. I know the end result will never change and we’ll be left twiddling our thumbs in a tidepool, wishing for more. But that’s okay, isn’t it? I… I can’t let go yet, Hitoshi.” He releases a shuddery sigh. “So… please come back.”

The door opens. He hears Bakugou call out that Uraraka is keeping an eye on the halls – and that they need to get moving.

Everything starts to blur together into a distant mess of sounds and movements, and maybe Denki should be concerned about that, but instead all he feels is his heart sinking down, down, down. He thinks he’s stopped crying at least, loosely aware of the uneasy glance Bakugou shoots him as the other mechanic takes the stairs three at a time with a tarp bundled under one arm.

The tank is cool against Denki’s temple. He watches Bakugou and Aizawa lay the tarp at the top of the stairs, talking and gesturing to the hand-holds and to each other. Aizawa turns and says something towards the tank, then again a bit louder.

On the other side of the glass, Hitoshi looks up at the man, hesitating, then back to Denki.

“Kaminari,” Aizawa calls, his voice a warning.

Right. Right. Denki takes a deep breath and pushes away from the tank. He backs up and rubs at his wet cheeks. “G-go on,” he croaks to Hitoshi, motioning blindly up to where they wait for him. The siren doesn’t immediately move. “Go on. ” His gesture is more frantic this time.

And finally Hitoshi goes. There’s a rush of purple as he ducks low to the bottom, then surges towards the wall where he’d pulled himself up the day before. It’s more forceful this time. It has to be. He emerges with a rush of water, heaving his upper body and a solid portion of his tail over the edge, where he hits the tarp with a wet slap and a hiss of discomfort.

Aizawa gets Hitoshi’s arms around his neck while both the siren and Bakugou work to maneuver the bulk of his tail and fins onto the tarp. Yamada joins them then to wrangle the bundle down the stairs, leaving Denki to wring his hands and—and what?

“The door, kid,” Aizawa grunts, any patience in his voice diffused by the dig of Hitoshi’s claws into the back of his shirt.

Denki nods and hobbles ahead of them, holding the door open. He wants to reach out to Hitoshi as Aizawa passes by, but his limbs feel like they’ve been filled with lead. The next thing he knows he’s following their little secretive parade down the hall and into the docking pool room, where the siren had been first dragged up from the deep.

The panel blares insistently when Bakugou flips the switch to open the pool gate, and the machines underfoot groan into action.

There’s a brief pause in the action once Hitoshi is laid back down; Bakugou answers the phone by the pool’s access panel, shouting at security to say he’s looking into a reported issue, dipshit , and then don’t fucking send someone, they’ll just get in my way

Yamada waves Denki over. 

He obliges, stumbling to the beached siren’s side with legs even shakier than usual.

Hitoshi reaches out, upper half propped up on one scaled elbow, and snags a hand in Denki’s shirt. He’s saying something but outside the water his language isn’t as fluid, as clear. Worse yet, he’s paling quickly with the lack of water to his gills.

Denki’s struggling to lower himself when suddenly Hitoshi pulls him sharply off-balance. The flash of panic vanishes when he’s caught carefully against the siren’s chest, cradled sideways, feeling the other’s rapid heartbeat through the cold, damp skin. Aizawa mutters something but Denki can’t hear it over the deep, gentle warbling from the being beneath him.

It starts his tears all over again, and try as he might to find words, they don’t come.

Too soon, the gate clanks fully open. Hitoshi’s gaze is an inch away, somehow sharp and soft simultaneously. Denki finds himself carefully rolled onto his back; Hitoshi’s forehead meets his for one timeless moment before pulling away.

Please come back.

The siren’s form slides gracefully out of view. Then, with a splash, he’s gone.



Denki doesn’t know which of the others eases him up to sit. He hears sniffling—Yamada? Maybe. Not important.

But it’s Aizawa who sighs, “I’m sorry, kid.”

And they both hold him as he breaks.

Chapter Text

Despite attending the mess hall for lunch for the first time in three days, it’s like Denki never left. In fact, more than one person appears surprised when he apologizes for the absence. He’s pretty sure they never noticed he was gone. When he excuses himself from the table with a shaky voice and unconvincing smile, he’s unexpectedly steered by Bakugou—who never shows up for mealtime—to an out-of-the-way table. They eat together mostly in silence, but Denki’s just fine with that.

When the time comes to go back to work, the other blonde side-eyes him and grunts, “Don’t even think about it. We’re taking the afternoon off.”


“You think I didn’t notice how distracted you were this morning? Fuck, Creaky, you started blubbering up at the sight of the anti-vapor spray.”

Denki lowers his gaze to his lap. Yeah, that had been pretty bad. “Sorry.”

Bakugou scoffs. “It’s – it’s whatever. But I can’t work when I gotta keep an eye on you so you don’t shock yourself stupid or something, idiot.” Then before Denki can get out another apology, he continues: “You got a T.V. in your room, yeah? One that’s not shit?”

It’s impressive in itself that Bakugou’s trying to make reasonably friendly conversation at all, so Denki is caught off guard—again. “Yes,” he answers lamely.

“Good. I’m bringing over my Switch, we’re gonna play Smash.”

The afternoon ends up not being at all what Denki expected; it’s actually pretty great. Bakugou’s a hypercompetitive beast but his running snarky commentary against both Denki and the AI is worth its comedic weight in gold. When they team up to take on two of his friends online, the guy commends him for being a good distraction for their enemies, and Denki’s certain that he should consider that top-tier praise. Maybe he could engrave it in steel and hang it on his wall.

In the evening, Bakugou fires off a few texts – and shortly thereafter Uraraka is at the door with three dinners in one hand and a USB full of movies in the other. They agree on a Ghibli marathon (well, Bakugou doesn’t, but he stops grumbling when Uraraka levels him a Look) and by the time they’ve made it through Nausicaa and Howl’s Moving Castle, they’re little more than a pile of limbs and pillows and crumbs strewn haphazardly on Denki’s bed. At some point Bakugou had pulled a small bottle of rum from who-knows-where, which it turns out has the surprising effect of mellowing him significantly.

As Uraraka scrolls through the list of movies to choose from next, Denki spots one title that makes his heart catch in his throat. Without further consideration he blurts out, “Ponyo.”

Uraraka squints at him. “Um… are you sure, Kami?”

No, he should say. Don’t listen to me, don’t play it, it’s a terrible idea. But his masochistic streak takes the reins and murmurs, “Yeah! It’s just a movie, it’s fine.”

She gives him a doubtful look. “Well… I don’t know. Wouldn’t it be a little too—”

“Just put it on, Cheeks,” Bakugou says. “He’s gonna have miserable little bitch moments anyways, might as well let them be when we’re here to help set him straight.”

That’s… astoundingly thoughtful, in the other man’s awkward, aggressive way. Denki stares blankly at his coworker—friend?—for a long moment, before grabbing the rum bottle and taking a swig himself.


“Thanks, man.” Denki pushes the bottle back at him and leans against the pillows with a sigh. “You heard him Uraraka. Let’s put it on.”

She puts it on.

He’s not fine. In fact, he’s an exceptionally miserable little bitch through the whole second half, chest aching and face red from tears as he puts himself in Sosuke’s shoes. Why couldn’t he and Hitoshi find a way to make it work? Why couldn’t they have a happy ever after?

Bakugou shoves a pillow at him and throws an arm loosely over his shoulders at some point, and soon Uraraka is curled up at his side. She’s too small, and he’s too warm, but he appreciates the gesture nonetheless.



Four days after the guppy’s release, Shouta finds himself on the ship’s deck for the first time in… he doesn’t know how long, to be honest. Staring out across the seemingly-endless vista of blue hasn’t brought him peace in years. Now’s no different.

He fights the desire to throw himself over the side of the ship and dive deep, past the reaches of the sun’s light and warmth. Entering the tank had been bad enough. If he were to touch the sea in its infinity, he’d be a goner, fins or not. He doesn’t want that; if he could just live alongside the water without the primal need to return to it, he and Hizashi could breathe easier at night. Especially at a time like this.

But the fickle magic still inside him itches, burns, more demanding than it has been in decades. So he loosens his grip on the railing and backs away to a nearby bench.

Hizashi joins him not soon after, taking a seat and slipping a hand into his. “Why are we meeting up here, Shou?”

Shouta tosses words around in his brain before answering, hoping to find the least alarming way to share the news. “I overheard some rumblings from the Applied Magic division this morning. They’re picking up small surges of power in the northern region. At the barrier’s edge, but they don’t know that.”

“The barrier?” Hizashi frowns. “Does that mean…?”

“He’s found the old settlement’s protected zone, yes. Been coming and going at his leisure by the sounds of it.” He huffs a sigh. “Wish he wouldn’t be so obvious. Someone’s going to think to watch that area soon.”

Hizashi’s staring at him, mouth agape. “Hold on. You’re telling me Hitoshi stuck around and hasn’t tried to get in contact?” There’s disappointment, maybe even hurt, growing in his gaze. “I was… so sure that they were meant to be together.”

Shouta shuffles in his seat. “I may have given him a bit to think over.”

The gaze on him turns hard; he can feel its sting, can even feel some of his husband’s vexed disbelief in his own mind. “Meaning what ...?”

“He wants to protect the ley-line. I explained the difficulties that a relationship with a human would bring to that.”


“He needed to know to make an informed decision—”

“—should’ve let them work it out—”

“—and I didn’t want him to throw his dreams, his goals, everything, away for what could just be a fleeting crush , Hizashi!”

The prolonged silence that follows lets Shouta know he fucked that wording up.

Hizashi’s lips purse. “Throwing away everything, huh?” His words are breathy and soft, all wrong. The mental connection between them floods with hurt and guilt.

“You know full well I’m not referring to us, ‘Zashi,” It’s not the first time the discussion’s come up in the past century. But ever since accidentally letting slip one night long ago that he himself hadn’t known the consequences of his choice before making it, the topic has been rough.

Hizashi’s expression remains pinched.

Shouta sighs; he supposes that this whole issue has brought the uncertainty back tenfold. Squeezing his husband’s hand, he murmurs, “I still don’t regret my decisions. I told Hitoshi that, too. But Hizashi… if he made the sacrifice and then changed his mind, or something went wrong… and I hadn’t said a word…”

Hizashi wilts at his side. “Okay. I can understand where you’re coming from.”

They’re silent again, listening to the waves and the gulls and the low thrum of machinery. It’s still not very peaceful to Shouta, but with his mate at his side, it’s easier to relax.



It takes Denki nearly a week to find some semblance of routine again, but when he does, he throws himself into it. He can’t keep stressing and wondering, it’s not healthy.

Yamada makes time to track him down at least once a day. They talk about little, pointless things, never mentioning him. Denki doesn’t know if that’s better or worse. He’s only seen Aizawa once since that night, and although the man had looked ready to ask a question, he’d stayed quiet. Simply… nodded. And that was it.

At the end of the week, just when he’s ready to stop hoping for some kind of miracle, a request comes through the technician task queue that makes his blood run cold.

Salvage Footage

Rover attacked near northern ridge of plateau - operator believes creature caught on video feed prior to exterior damage - reports vivid plum-colored scales and fins that do not match known mundane sea life nor magical fauna native to this area - please attempt to salvage and/or copy the video footage for further investigation - discretion requested.

Well, fuck that.

He’s got his phone out in shaky hands before even bothering to check the rest of the queue.

professor yamada, he was seen

what do we do


Denki looks over at the rover. Its front end is battered quite impressively considering that the machines are built to be solid enough to withstand mid-sea pressure. The small attachments usually fastened to the sides are all either missing or mangled; it’s an expensive loss. The camera itself is shattered, but the memory for it should be secure, deeper in.

His phone buzzes; a call, rather than a text. He swallows before answering. “Hel—”

“How do you know that?” It’s Aizawa, more alert than Denki’s ever heard him.

“A request came through my queue. It’s— it’s him, I know it, even if it’s vague—”

“Read it to me, Kaminari.”

He does, voice a bit shaky, but the man on the other end doesn’t comment on that. In fact, he’s quiet altogether for a long pause after Denki’s done.

“Who made the request?”

Denki skims the message. It’s a name he doesn’t recognize. “U-uhh, some guy called Okuta Kagero?”

Aizawa swears under his breath. “Kid, destroy the video. Use whatever you think will work. I have some things to take care of on my end. If the workshop has a drone available, get it ready. I’ll get in touch again shortly.” And then he hangs up.

Denki’s never been good at magic tricks or misdirection, but when it comes to destroying electronics beyond even his own repair, he’s a pro. Maybe he shouldn’t be so eager to zap the memory chip until it’s fried, but chances to play with electrical currents are few and far between, and this is for the best cause he can possibly imagine. One short-circuit later, he’s confident that the recording is gone for good.

It’s then he notices a message from a few minutes past:

Meet us at the hull, bring the drone. 



Aizawa doesn’t look at all comfortable. The man’s casting side-glances at the water as if he expects it to rise up and grab him any moment, while simultaneously fiddling with what appear to be several knotted strings attached to a loop. Beside him, Yamada holds a stone with a hole bored through it. He at least looks happier.

“Hey. What’s the plan? How can we throw them off?” Denki asks, setting aside his cane to fetch the drone out of the box. “Just so you know—this isn’t waterproof.”

“It doesn’t need to be. It’s just a delivery vehicle,” Aizawa grumbles. “For this.”

The collection of strings is… unimpressive, honestly. If Denki didn’t know the man better, he might guess that it’s just a frayed net, discarded and thrown away. Each string is knotted at different spots along its length, some more intricately than others, and a few have what seem to be fragments of shell and beads tied into it as well.

Before he can ask, Yamada leans in, stroking along one of the strings reverently. “A mer message,” he says with a smile.

“A warning.” Aizawa’s fingers deftly tie another bump in the last string. Then he takes the stone from Yamada and feeds the master loop through it, tying that off as well. “Hitoshi will likely be more cautious now that he’s been spotted, but that’s not enough. Destroyed footage won’t prevent follow-up.”

Denki swallows. “You think they’re going to hunt for him?” Like an animal. He gets the mental image of harpoons and nets, Hitoshi’s snarls and fear, and very nearly loses his breakfast. “They—they wouldn’t hurt him—couldn’t—could they? There’ve been treaties and laws in place, for like—”

“One hundred and seven years,” Aizawa answers automatically, voice low.

Yamada settles a hand on his husband’s back.

Once handed the strange rock-and-string creation—(a message?? He has so many questions)—Denki secures it to the graspers of the drone. “So we just drop this and wait for him to find it? How do we even know he’s in the right area?”

“It’s an estimate. We’ll lure him to it.” He pulls out a switchblade, then hesitates, and hands it to Yamada. “My blood…” he says, then clears his throat. “…he won’t recognize it.”

Of the three of them, was Aizawa really the only one who hadn’t been bitten or sliced? Denki’s own injury had been obvious and quite the cause for panic, and he distantly recalls the scrapes on Yamada (and everyone else in the water, for that matter) from wrangling Hitoshi into the tank the first day.

Yamada takes the knife with a grimace, looking nauseous.

“Use mine,” Denki says, before he can regret it. “I get cut up at work all the time anyways, it’s nothing. Plus he’ll definitely recognize mine, yeah?”

There are no protests. A minute later, the strings are splattered with red and Denki’s holding a cloth to his elbow to stop the bleeding. He watches Yamada inexpertly navigate the drone with its package far to the north, until the controller beeps a distance warning some three miles off. The ‘message’ is released to sink deep into the ocean below.

“And now we can only hope he gets it,” Yamada sighs, reversing the machine’s course until they’re able to retrieve it at last.

It feels too… simple. Not enough, just as Aizawa had said earlier. The thought of sitting around on this ship tinkering while Hitoshi might be putting his life at risk nearby is—

“Hold on,” Denki says slowly. “Why is he still this close? I know he can’t go home but the plateau is so shallow, there’s nowhere for him to hide!” A note of anxiety creeps into his voice unprompted. “What did that knot warning mean? We need to be specific—”

Kid. Calm down. There’s nothing we can do at this point except wait.”

Yamada sighs. “He’s worried, Shou.” A pause. “Kaminari, you mentioned the laws that protect mythical beings earlier. Do you know what event made them come about?”

He wracks his brain, but those high school history classes were too long ago. He shakes his head.

“Hizashi…” Aizawa grumbles.

“Love, I’m putting my foot down for this. You helped out your parallel protégé.” Yamada clamps a hand down on Denki’s shoulder and steers him towards the door. “And it’s high time I did the same for mine!”

Protégé? Denki thinks weakly as he’s escorted down through the ship to the bunk cabins. Yamada is a constant source of chatter the whole way, explaining the history of the old merfolk settlement of the Ogasawara Plateau. Its residents weren’t sirens like Hitoshi, but another subtype of mer known as ‘coral-fins’—smaller, brighter, and far less aggressive than their trench-dwelling kin.

“Hitoshi didn’t seem too aggressive,” he murmurs as Yamada fiddles with the door.

“No,” Yamada agrees. “But there are reasons for that. Come on in.”

It feels like stepping into a curiosities shop. For a three-month expedition, the pair have gone all-out, lining the walls of the common area with countless shelves. Each is filled with baubles and oddities of all sorts – jars of sea-glass, pottery both cracked and pristine, carved idols, semi-precious gemstones in heaps, stunning shells, and plenty of suspended string-messages like the one they’d dropped into the sea. Interspersed between the displays are various books and what appear to be hand-written journals.

Whistling, he turns in place. The collection really is impressive. “Nice treasure hoard,” he jokes.

“…Thank you,” Aizawa responds, to his surprise. The dark-haired man walks past and disappears into an adjoining room wearing an expression halfway between irritation and sheepishness.

Yamada steers Denki down onto one of the couches before plucking a pair of textbooks off a nearby shelf. “Don’t mind him. He’s not good with certain discussion topics, no matter how much they need to be addressed. But we can’t keep skirting around your involvement, can we?”

The upturn in volume at the end of the question leads Denki to believe that it’s not just meant for him. “Uhh… no?”

“No indeed. Unless you’ve changed your mind about protecting Hitoshi at all costs.” Yamada’s pale green gaze spears him to the couch. “But I don’t believe that’s the case.”

Denki’s breath leaves him in a rush. “I’ll do anything.

The professor’s intensity washes away like a tide over sand, leaving behind a wide grin. “I knew I recognized a kindred spirit in ya, Kaminari! You remind me so much of myself once upon a time. Speaking of…” he slides one book over, and his voice turns serious again. “The event I alluded to, the one that heralded the laws. Hits close to home, wouldn’t you say?”

The title before him reads ‘Genocide at Ogasawara: pre-treaty extermination of merfolk for magic’.

Denki rereads it three times before the reality of the title hits him like a punch to the gut. “Here? This settlement is what brought about the protection acts?”

After weeks of working in close conjunction with historians and researchers, he’d picked up on some of the old beliefs surrounding the mer, ideas formed when anything non-human was feared, envied, and treated like a beast. Among those was the nauseating theory that consuming mythical creature parts grants power—long since disproved—and that magical beings guard ley-lines to gatekeep humans from deserved ascension.

It’s no secret that Ogasawara Plateau once boasted one of the strongest ley-line paths in the Pacific—that was a fundamental interest of the expedition, after all—but it had never occurred to Denki that it might have brought about the disappearance of the local mer.

No—not disappearance. Slaughter.

Hizashi slides a bowl of ginger candies across the table to him. “The mer themselves are protected these days, as you pointed out. The laws defend magic-inherent populations globally, and was a brilliant step forward for relations between the mythical and mundane. But it can’t rewind the bloodshed on the plateau, and it specifically doesn’t protect that which the mer hold dearest. What they’re compelled to defend.”

Denki leans back, head swimming. “The ley-line. But—this one’s dead, I thought.”

“Not dead, Kaminari. Dormant. For over a century, certainly, but various sources believe that something big is about to come from it very soon.” Those green eyes glimmer.

Denki may not be a genius, but he can connect the dots just fine. “That’s why Hitoshi stuck around? He’s drawn to the ley-line waking up.” It makes more sense than staying for Denki’s sake, especially considering the siren hasn’t come to visit.

“Magic calls to magic,” Yamada says. “Shouta and I think he’s found the heart—that is, the chamber that gives shape and life to Chaos. He felt it pulsing earlier than the rest of us. But once the ley-line wakes up entirely, others—non-mer—will clue in. He’ll fight them to keep it safe, if he has to. That primal compulsion runs deep.”

Goosebumps crawls over Denki’s arms. “Fight them alone?”

“Not if we can help it,” Aizawa murmurs from the doorway, arms crossed.

Looking between the two of them, Denki can’t help but feel like he’s being tested. Yamada’s leaning towards him, bright and encouraging, a due contrast to the doubtful and guarded posture of his husband only paces away. There’s a kind of untouchable static that hangs in the room, eager to snap, building pressure. But towards what?

His mind turns to Hitoshi; dangerous, beautiful, fascinating, powerful Hitoshi. The thought of him hurts like an open wound, inexplicably raw despite the short time they’d spent together. It doesn’t make sense; none of the others seem as affected, as displaced from who they were before. It’s as if Denki’s life has been split into two defining halves, neatly bisected from the moment Hitoshi had said his name. A paradigm shift that’s left him floundering, lost, with only one light to guide his way.

“Please.” Denki swallows thickly, turning so he can face the two of them, folding his hands in his lap and dipping his upper body respectfully, desperately. “I know I’m just a kid to you. I don’t even know what use I can be. A-and maybe it’s weird that I feel so strongly about this, but I do, like I’m being compelled.” Heat burns in his eyes. “So please let me help. Let me fight with him, for him, however I can!”

He’s swept into Yamada’s hug at the first shuddery sob, and just lets it happen, giving into an encore of the pain from a week prior. This time, at least, he’s able to stay grounded, listening.

“Notoriously stubborn heart-thieves, aren’t they?” Yamada says softly. “I knew it was more than a crush. Your pain looked too familiar.”

Denki glances up, confused.

But his question is interrupted by Aizawa kneeling down beside them. The scruffy man’s eyebrows are tight and low, the line of his lips apologetic. “It seems I made an error in judgment. I wouldn’t take back my cautions to Hitoshi even if I could—they’re still important, regardless—but I am sorry for doubting you, Kaminari.”

Yamada continues. “I’m sure when his goals have been met, when there are others to help protect the ley-line, he’ll leave the sea for you if you ask. Until then, of course you can help—”

“Hold on, no,” Denki interrupts, pushing back from the man and swiping an arm over his own eyes. “What? Leave the sea?”

The ticking of the wall-clock fills the brief silence before Aizawa murmurs, “If he chooses to give up his magic, Hitoshi can live with you on land. Functionally, that is. Like a human.”

At first, Denki thinks of Ponyo , and the miserable prayer he’d made curled around a pillow with his friends bracketing either side. This was the chance he’d asked for, wasn’t it? Some small miracle to make it all work out.

But that was before he’d learned about the imminent magical surge and Hitoshi’s determination to safeguard the ley-line once and for all. A renewed purpose, following the near-eradication of his people. A goal which would no doubt require every bit of magic the siren could muster.

“I would never ask him to do that. I don’t want to make him choose.” He steels his shoulders, meeting Aizawa’s gaze. “We’ll make it work some other way. As long as I know he’s coming back to me… I can be happy.”

Aizawa, in a rare wide-eyed display, merely blinks.

Denki finds himself tugged unceremoniously back into a hug by the more emotive of the pair, Yamada blubbering something that sounds remarkably like ‘can we keep him, Shou?’ , along with scatterings of praise and other reassurances. He laughs and pats the tall man’s back awkwardly.

“Really, it’s— it doesn’t take much.” He looks at his hands. “My stuff on the mainland’s in storage. Nobody’s waiting for me back there. Chichijima could probably use another mechanic, right? And then when I’ve saved up enough, I’ll buy a boat to live on the water as much as I can.” He’d been writing ideas of the sort in the margins of his workbook all week, figuring out the logistics of a dream. But... there was one hang-up. Denki frowns. “The language barrier is the kicker. I dunno know how to approach that.”

Yamada chuckles, and lets him go with a sly glance at his husband. “I think we can help in that regard. Shouta’s something of a natural.”

Said husband looks thoroughly unamused. “Spell it right out for him, why don’t you?”

“Come on, love, he’s going to learn sooner or later!”

“Then let it be later.”

Denki stares at him. “You know how to speak their language?”

“Oh yes, rather fluently,” Yamada says, suddenly far too jolly. “We’ve had quite some time to teach each other, little listener. You see, he and I were also hopelessly smitten and facing that same barrier, once!”


“It’s technically later, dear.”

Denki tunes out their bickering in favor of letting the puzzle pieces come together. They do so awkwardly and with great difficulty, like a toddler mashing a square block into a circular hole until it somehow defies logic and physics to pass through. And pass it does, because he’s suddenly picturing Aizawa with horns, fins, and a tail, and it… isn’t completely unbelievable.

Actually, as the seconds pass by, it starts to make sense. A small part of him thinks that maybe he should be more surprised by this revelation, and yet that part is dwarfed by relief and—dare he say hope?

“Okay… alright. I have… so many questions,” Denki mumbles, catching both sets of eyes. “But for now, just… does Hitoshi know?”

Aizawa, caught in a smothering and seemingly pacifying hug from behind by his toothpick of a partner, just sighs and nods.

Denki huffs out a laugh, eyes wet. “That’s—that’s great. Shit, man. He’s not alone.”

Once again, the man appears taken aback. “Pardon?”

“I said he’s not alone. ” He chokes back his tears; at least they’re happy ones this time. “I kept thinking how sad it would be to have nobody to talk to—let alone relate to. But he has you!” A strike of realization hits him, and he laughs again, leaning back as if allowing relief to flood through his whole being. “So you’ve already chatted with him then, yeah? Kinda jealous, not gonna lie. What’s he like, really?”

There’s a strange roughness to Aizawa’s voice as the man retorts, “He’s a brat.”

Denki’s grin is borderline painful. “Sounds about right.”

“Shouta’s attached,” Yamada supplies gleefully.

The other man doesn’t try to deny it, merely rolling his eyes before speaking again. “That aside, the issue of contacting him still stands. I’m confident he’ll find the warning, but he still can’t approach the expedition ship safely. One-sided feedback won’t be enough.”

The giddy high comes to an abrupt, sobering close. Right, there’s still the matter of actually helping the siren. Words wouldn’t ward off greed.

“That house-boat I’m gonna save for would be great right about now, huh,” Denki mumbles. “Don’t suppose one of you has one laying around?”

Aizawa shakes his head.

His husband, however, taps his chin. “ We don’t… but…” He twists his lips thoughtfully, giving Aizawa a side-eye stare. “Shou… she can help.”

The dark haired man’s puzzlement lasts a solid five seconds, before his brows slam down close over a sharp glare, a muscle in his cheek twitching. “No. Absolutely not.”

“She’s your friend! I know it’s been a while, but she did offer a favor...”

“‘Zashi, last time she also tried to eat you.”

Yamada waves a hand flippantly. “It’s been what, half a century? Forgive and forget! Besides, what other options do we have?”

It’s almost possible to see the gears clicking and whirring in Aizawa’s head, searching for any possible positive answer to that question. Denki stays silent, wondering whether he should take that last exchange with a grain of salt or be thoroughly worried.

By the way the ex-siren’s shoulders droop, he’s got a feeling it’s the latter.

“I don’t like it,” he growls. “But you’re right. Give me the phone.”