Izuku was absolutely over the moon that he was able to call himself Katsuki's boyfriend. Every kiss sent his heart racing and caused him to lose his breath, both from the overwhelming joy of getting to kiss his Kacchan, but also from the sheer intensity of the kiss.
He knew he was lucky to even get to kiss Katsuki, Izuku didn't take it for granted at all.
However, he found himself getting maybe a tad bit fed up with bleeding lips, traumatizing tongue use, and the painful clacking of teeth that he was sure was going to cause a cracked tooth sooner or later.
Every kiss with Katsuki was like asking for a drink of his saliva. So much of Katsuki’s spit filled Izuku's mouth that Izuku feels like was staying well-hydrated from their make-out sessions alone.
It was adorable—and still is! Izuku would always treasure the clumsy, eager incompetence of inexperienced Katsuki—but enough was enough. Izuku was determined to teach Katsuki how to kiss, in a manner that would result in absolutely no more unintentional bleeding orifices, excessive exchanges of saliva, and, most importantly, in a way that didn’t leave All Might cringing and running away when he saw them together.
Izuku still struggled to meet his eyes after being walked in on in his dorm room with Katsuki in his lap and mouths connected that one time.
Of course, though, that was easier said than done.
Even approaching Katsuki about the subject was difficult enough. It wasn't like he could just go up to Katsuki and say ‘Kacchan, you suck at kissing. Like, you’re adorable but also... absolutely awful. Can I show you how it’s done?’
Well, not if he wanted to keep his boyfriend, at least.
Izuku decided to start by simply hinting it through his actions during their daily make-out sessions.
He tried to gently pull away from Katsuki, but Katsuki’s firm grip of his face kept him in place. Any resistance just made Katsuki pull him in closer and slobber on him even more, like a dog afraid to lose his bone.
When Izuku tried to take control of the pace, but Katsuki got more aggressive.
Izuku tried to copy Katsuki’s motions, sticking his tongue out sloppily and waggling it against Katsuki's teeth just as Katsuki had moments prior, trying to show how weird it felt, but Katsuki didn't get the hint. He just bit Izuku's tongue.
Nursing his throbbing tongue, Izuku decided he had to come up with another plan. He needed to be more direct, use his words.
So he brought it up with his friends when Katsuki joined them at lunch.
“Uraraka, have you ever kissed anyone before?”
Uraraka spat out her drink. She turned red, coughing as she tried to regain her composure. “W-what?! Why are you asking?!”
Izuku saw her eyes flicker to down the table. He followed her gaze and caught Asui's composed, watchful eye, and understanding hit him.
“Just wondering,” he replied, sheepish. Izuku decided not to press and instead turned to face Iida.
“Iida, how about you?”
Iida chopped his arms disapprovingly. ”As of this current moment in my life, I do not take any interest in such unsanitary displays of affection, nor am I willing to endanger my oral hygiene!”
Izuku blinked. “That’s completely understandable,” he nodded. He turned to the next person at the table.
Todoroki stared silently, deadpan. Izuku met his eyes, and they stared at each other silently before Todoroki lifted an eyebrow. Izuku nodded in understanding.
The next person was Aoyama, who was very obviously and very eagerly waiting to be asked, near-vibrating as he beamed. Metaphorically, that is. Izuku hesitated. Did he-- or any of them, in all honesty, want to ask about Aoyama's romantic experience?
Luckily, Asui closed that can of worms for him. “I have kissed before. Gero.”
Izuku peered at Uraraka out of the corner of his eye. He barely resisted the urge to face-palm when he saw her pitiful attempt at acting normal. That was not subtle, dammit! “Y-yeah?”
“Yeah." Asui cocked her head at him, blinking curiously. "Why are you asking though? That's an odd topic for you to bring up. Gero.”
Izuku bit his lip. How should he word it to let Katsuki know being so aggressive was unnecessary?
“Just... wondering how different people kiss,” he said dumbly.
Katsuki slammed his hand on the table, leaning into Izuku’s space with a dark look on his face. “Oi, you piece of shit nerd, are you forgetting that you already have someone to do that shit with?” He growled, annoyed.
“A-ah, no! No! Not like that, Kacchan!” Izuku flailed, shaking his head wildly. “I-I mean, more like interesting techniques! And special... skills! You know, so we can power up our kissing level! Add some spice to it! Plus Ultra and all, y'know? The grind never stops!”
Katsuki frowned but leaned back with a dissatisfied grumble. “Once a nerd, always a nerd,” he huffed. Izuku exhaled a sigh of relief.
Iida frowned. “Adding spice to your canoodling sessions would inflame your lips severely and I do not recommend—“
“Not literally, Iida,” Izuku sighed.
Other than making Katsuki think Izuku wanted to cheat on him, his idea of bringing the topic out in the open didn’t do anything. If anything, Katsuki got more aggressive, making sure to bruise Izuku’s lips even harder, twice a day.
Finally, Izuku decided enough really was enough and resolved to speak to his boyfriend about it openly and honestly as he should have from the start.
“Kacchan’s kissing is cute but—but it’s not good for my lips,” he blurted when Katsuki sat on Izuku’s bed after class, leaning in.
Katsuki froze before frowning. He clicked his tongue before reaching into his pocket and pulling out a tube of lip balm. “Fine, Deku, you can have this.”
Izuku stared at the cinnamon fire lip balm he’d been handed, grimacing. So that's what that flavour on Katsuki's lips was.
Katsuki leaned in again, hand coming up to fist Izuku’s hair, but Izuku leaned back, dodging the kiss and touch.
“W-wait! I, uh, was just wondering, Kacchan, do you think it might be possible that we could potentially, perchance just, uh, I was just thinking we might, or perhaps should, if you would be willing—“
Katsuki scowled. “Spit it out!”
Izuku stammered, trying to think of how he could say it without offending his boyfriend.
“—just a suggestion, we don’t have to—“
“If you don’t want to kiss me anymore, just say it, dumbass.”
Katsuki retracted his outstretched hand and sat back, leaning away from Izuku.
“You’ve been acting weird for a while. Did you think I wouldn’t notice, shitty nerd?” He scoffed at Izuku’s look of surprise. “And then bringing up kissing others, and now—“ Katsuki paused, looking at the distance between them.
“If you hate kissing me that much, just say it, you useless Deku.”
The hint of hurt in his hostile tone was like a dagger to Izuku's heart.
Katsuki leaned further away, face settling into his neutral scowl, trying to act like he didn’t care.
“Kacchan.” Izuku reached out, but Katsuki swatted him away, refusing the touch.
Izuku bit his lip, hesitating a moment. He grabbed at Katsuki again, not letting go when Katsuki tried to shrug him off, making Katsuki scowl and glare at him.
Izuku stared Katsuki in the eye. “That’s not true, Kacchan. I do like kissing you—a lot! Way too much. Embarrassingly too much.” He scratched his neck sheepishly. “But... you’re right.
“You’re right that I’ve been acting weird... Kacchan, I’m sorry,” he placed his hand on Katsuki’s cheek softly, cupping it, watching Katsuki blink in surprise. “I should have just been honest with you from the start.”
Katsuki’s frown returned. “Haah? What haven’t you been honest about, shithead?”
“I-I love kissing Kacchan and touching him and being close to him,” Izuku mumbled, cheeks reddening.
It was still new and embarrassing to admit his feelings for Katsuki this way, after years of thinking he was doomed to an eternally one-sided love.
“But I want to try it... another way?”
Katsuki frowned, innocently confused. “What else is there to try? We do the tongue shit and all. Teeth, lips, biting, and sucking.” He checked the items off his fingers as he said them aloud.
Izuku wondered who or what in the world took advantage of Katsuki’s naivety and taught him that that was what kissing was. No wonder Katsuki had been so hesitant when they first started making out. He was probably expecting a... dog mauling session instead of... the heat of a fire melting two candles standing side by side, until all that remained was a pool of their wax, mixed and blended together until they were one.
“Err... yeah. You’re not wrong. But maybe just,” he paused. “Can I show you? Just follow my... lead?” He offered tentatively, knowing better than to expect backlash from the suggestion—Katsuki had grown immensely since their days of young—but habit making him hesitate anyways.
Katsuki huffed but didn’t disagree. “Tch. Fine. Show me what it is.”
Izuku grinned, swooping in to press a quick kiss against Katsuki’s cheek. “Thank you, Kacchan!” He swiftly avoided Katsuki’s startled explosions as he flushed.
Izuku brought his hand up to cradle Katsuki’s cheek, rubbing his thumb against it tenderly, a stark contrast to the way Katsuki would almost pull Izuku’s cheeks off.
Katsuki blinked at the touch and leaned in, teeth bared, ready to bite, but Izuku pulled back. “Follow my lead?” He reminded gently.
Katsuki grumbled but acquiesced. Izuku leaned in, pressing their lips together softly, a bare brush of lips that lingered like the brush of velvet against skin, a new sensation for Katsuki, who was used to their earlier violent clashes. Katsuki leaned in, but Izuku pulled back.
Every time Katsuki chased his lips, Izuku moved back, and Katsuki quickly caught on. Eventually, Katsuki begrudgingly accepted the soft presses as Izuku gave them and so Izuku began to move his lips against Katsuki’s.
Katsuki was quick to take that as a challenge and moved to bite Izuku’s lips. Izuku pulled back.
“Think of this as... partner yoga. Not weightlifting,” he explained. "We move together, in harmony, and push ourselves to our limits that way."
That explanation only annoyed Katsuki, but Izuku dove back into the kiss, this time playfully pulling at Katsuki’s bottom lip.
Accustomed to harsh, unforgiving bites, Katsuki was confused by the gesture, but as Izuku continued to nibble softly, flicking his tongue against Katsuki's tranquilly, Katsuki attempted to reciprocate.
Slowly, Izuku introduced new aspects of kissing. How to use tongue, press them together, swirl them and invade one another's mouths without drowning the other in spit. How to nibble and suck in ways that wouldn’t leave you bruised and bloody, but teased, aroused, and stimulated. How to tilt your head and lips in time with each other and one another, to move in harmony, let their bodies mix like two streams of water converging, rather than clash and bump at every angle.
He showed how to use hands to touch and pull the other closer, to grasp at and tug at each other's scalps in ways that excited, brought heightened pleasure to their movements instead of causing injury, and, the main lesson: how to make your partner go heady and breathless from the press of your lips against theirs.
Izuku pulled back, taking in Katsuki’s flushed appearance, his breathless panting, and reddened lips. Katsuki looked absolutely delicious, positively edible. Izuku wanted to continue making a mess of him, teaching him all kinds of new things. He wanted to make Katsuki make more noises, more soft gasps and sighs and sounds of contentment. He wanted to push Katsuki down and continue their lesson.
Katsuki clearly wanted the same, leaning in as his eyes fluttered shut, lips parting as he tried to connect their lips once again, waiting for Izuku’s kiss.
It was so cute that Izuku couldn’t help but connect their lips for another brief moment, but he had to separate soon enough.
Katsuki was confused when Izuku pulled away. He frowned, his breathless, flushed appearance and swollen lips making him look pouty instead of angry.
“Why did you—“ Katsuki stopped, looking away, cheeks red, before meeting Izuku's eyes with a pouty glare. “What was that?”
“What was what?” Izuku asked, absolutely enamoured by Katsuki’s kissed-silly appearance. He was breathless all over again.
"That. You know. What you just did. With all of the. The kissing stuff.”
“Oh,” Izuku said, unable to hide the grin in his voice. “That was just, uh, 'different' kissing stuff.”
He resisted the urge to say ‘normal for anyone who wasn’t raised by wolves’.
Katsuki scowled, the sheen on his lips making Izuku want to return there, return home. “The hell? That shit’s weird,” he grumbled, face still red. Katsuki glared at Izuku.
“You’re not allowed to get better than me at things,” Katsuki sneered, still blushing. “So I’m going to do it to—“ he paused, eyes flickering away, “—with you. Until I learn. And get better than you, shitty nerd!”
“Of course, Kacchan!” Izuku beamed. “We can do it lots! Practice makes perfect, after all!”
Katsuki huffed but didn’t refute that.
Feeling bold, Izuku leaned in, pressing a quick peck to Katsuki’s cheek. Laughing when Katsuki exploded into a fit of embarrassed explosions, Izuku couldn’t wait to teach him all he knew.