It started slowly.
So slowly in fact that Ichigo didn't feel like anything was different for a really long time. Or anyone else for that matter.
At first it was small things.
He would be more affectionate with his sisters, picking them up to hug them when he was happy, patting them on the head when he was proud, praising and complimenting them any chance he got. It didn't raise any warning, anyone could tell Ichigo loved his sisters, and if he was more clingy to the twins after two wars nobody could blame him.
The fact that Ichigo wasn't normally a demonstrative person was glossed over, near death experiences, especially in one so young, it changes you. And it wasn't like it was a bad thing.
Yuzu soaked up the affection, giving it back with enthusiasm and glowing with happiness. Karin would grumble at the hugs, saying she was too old for them, but secretly enjoyed having her Ichi-nii back and if she hugged him just as fiercely, well, nobody but Yuzu was there to see it.
The increased protectiveness was ignored completely because it was Ichigo, the only way for him to stop being protective would be if he was dead and even that wouldn't probably be enough ( he already died and came back to protect, he'll do it again, as many time as needed ).
People started to wonder at the growls.
Sometimes Ichigo would growl when frustrated or angry, not an annoyed grumbled but a real animalistic growl coming from the throat and vibrating on its way out. It was a deep sound and it startled people at first but soon Ichigo's friends would put that on the count of him being a weird hybrid.
Surely it was the hollow acting out a little when Ichigo's emotions ran high (they purposely ignored the fact his eyes never bleed black when the growls would occur or that his inner hollow wouldn't care about petty human problems).
After that Ichigo slowly gained a whole range of noises a human throat shouldn't be able to make.
He would trill when pleased or in a playful mood, croon and coo with fondness to his sisters ( his pack ) and sometimes his human friends too ( not pack, not anymore ), chirp when confused.
His growls became more various, from high hiss to deep snarl. Those he would only use on bad days and even then, when hollows interrupted his times with the twins ( pack bonding ).
The first time Ichigo hissed at a hollow ( intruder! ) before cleaving it in two so fast the sound hadn't died yet when he was done, he actually paused.
Then he thought about how he was really comfy, piled with his sisters on the couch, blankets and pillows everywhere, watching a mushy romance movie and basking in the feelings of home ( safe, pack, den ) when the hollow came too close to the clinic ( his territory, no one gets close to the den ).
In a single moment he was out of his body with a snarl on his tongue and bloodlust in his eyes ( kill the intruder, kill it, how dare it! ).
The twins didn't mention it when he came back and sprawled back between them with a croon. They didn't comment on the sounds or ask about what happened (they knew).
Nobody talked about the purr that came from Ichigo then, happy and content after protecting his family ( his pack, his den, his ).
No, none of this mattered to Ichigo because everything felt right and more often than not he wasn't conscious of the sounds, it felt like talking and was it really his fault nobody here could understand him? Grimmjow could when they saw each other for their weekly fight ( courting, they were courting ) they had wordless conversation all the time, it was so much easier to express himself with Grimmjow.
What registered in Ichigo's mind was the pain.
He thought of a stomach bug at first. Small random burst of pain gone so fast he could have imagined them.
He quickly dismissed it, Yuzu was always really careful with the food and they all ate the same thing so there was no way Ichigo was the only one sick. He didn't even eat out anymore these days, favoring groceries shopping ( providing for the den ) so Yuzu could cook the best meals.
Not a stomach bug then.
But the pain didn't stop, the painkillers where useless and Goat-Face told him there was nothing wrong with his body or his soul after a quick check up.
Soon the feeling of something missing came with the pains, like a small void, a tiny ball of pain and hollowness and he didn't know what to do. He could still function normally, could kind of ignore the feeling but sleeping was becoming harder and he couldn't let his health decline, he had to be strong for his sisters ( must protect the pack, can't be weak, have to e...! ).
He had a visit to Soul Society soon so Ichigo decided he was going to ask the 4th division for a health check. The pain and void had become so constant he could tune them out almost completely. He probably could have just ask Urahara but he didn't trust the man to not try and experiment on him, or even withhold the truth, the past had teach him that much about the shaddy shopkeeper.
He was halfway to the 4th barracks when Renji jumped him and asked for a fight. The move was so like Kenpachi, Ichigo couldn't repress a tiny hiss.
He still shrugged and accepted, he could really use a fight right now, he was feeling antsy ever since he stepped foot in Soul Society. He liked fighting Renji too, it's wasn't as good as his battles with Grimmjow but it was miles better than Kenpachi ( Red didn't want to mate him, pack bonding was good ) and if he was already fighting someone the crazy 11th Taichou knew to leave him alone. Small mercy.
At least if Isane didn't find anything wrong with him he had a good reason to go to the healer now, the fight was sure to leave wounds, he could reign in his high speed regeneration.
They got to an abandoned part of the Rukongai because their fight were always destructive on the landscape and soon enough they were in Bankai. Renji was bleeding from multiple cuts already, half his shihakusho shredded by Ichigo's Getsuga and he was panting harshly.
Ichigo had a few cuts and a nasty gash on his head that looked way worse than it was but he was still fresh as a daisy, his reiatsu cloak almost pristine despite the pain in his middle that took some of his attention away. His fights with Grimmjow were way more wild and Renji looked like a kitten in comparison.
With a trill of joy, Ichigo prepared a last Getsuga Tensho as Renji threw himself at the ginger. Their reiatsu clashed and something in Ichigo stirred to life.
It felt like the void reached and pulled, tendrils of Renji's reiatsu answered and soon all of the red-head energy from the attack was absorbed within Ichigo instead of dissipating in the clash. Without anything to block it anymore, the Getsuga followed it's course and cut Renji's left leg in an angry red line, the move too fast for him to dodge completely.
Ichigo panicked with the realisation, a keen escaped him as he fell out of bankai and ran to the Fukutaichou to check on him ( it's hunger, it's hunger, I need to eat, I can't, he's pack, what did I do!? ).
The ginger picked up the unconscious man and rushed to the 4th at his fastest Shunido. He waited just enough time to be told Renji was okay, that it was just reiatsu exhaustion and they should be more careful with spars in the future before he bailed.
Without thinking, he reached out, opening a Garganta and fell to the sands of Hueco Mundo and it's eternal night.
Ichigo took a moment to look at the moon and feel the reishi heavy air around him. There was always something about the place that relaxed him. Made him feel at home ( not den but it could be, should bring pack here).
Then he let out a high keen of distress because it wasn’t enough, he needed someone, he couldn’t process what he did to Renji ( his pack mate) , he needed Grimmjow ( his mate, he needed his mate).
Less than a minute after that the blunet stopped in front of Ichigo with a confused warble ( What is it? What do you need? ) .
A look at the ginger, taking in the blood and superficial cuts, how he seemed physically okay. Then he stopped on the other’s face, blue met brown and he immediately enveloped him in a hug, purring and crooning to sooth the younger male ( it’s okay, you’re safe, I’m here, you’re safe ).
They end up sitting in the sand, their blades around them, Ichigo in Grimmjow’s lap the sounds of purring filling the desert around them
His head into the crook of the other’s neck, Ichigo went straight for the facts ‘’ I ate Renji’s reiatsu’’ the words came out muffled and distorted but the Arrancar had no problem hearing them.
‘’ That’s the red-head one ? He part of yer pack if I remember right, that’s why yer freakin’ out on me? I’m guessin’ ya didn’t kill him or ya wouldn’t be here with me. ‘’ Grimmjow answered, petting the ginger’s back mechanically.
Ichigo turned his head to look into electric blue eyes ‘’ That’s the eating reiatsu part I’m freaking out about! I know I’m part hollow but I didn’t expect to want to eat souls! ‘’ he whisper yells with a whine so he doesn't hurt his m… Grimmjow.
The blunet chirped and nuzzled him, careful of the mask fragment on his jaw ‘’I’ll make a wild guess and assume ya evolved too fast. Yer already a Vasto Lorde but ya never had ta eat a soul ta get there and now that yer getting even more powerful ya probably need the fuel ta balance it. Yer plenty hollow enough so I ain’t shocked ya need souls now’’
The hybrid leaned into the Arrancar with a pleased rumble and a contented sigh ‘’Okay’’ he said, simply.
He trusted Grimmjow, even more when it was about weird hollow biology. After all, it was thanks to him he didn’t freak out about the sounds and the nesting. Any time he would wonder about them, Grimmjow would respond in kind during their play fight, unknowingly reassuring the ginger that it was normal hollow stuff. If he had known the pains came from this side of him too, he would have come to his mate sooner.
And wasn’t that a thought. His mate. Because he was, he knew that know. He had no idea how it happened when they never even mated but somehow he considered the Arrancar his as much as he was Grimmjow’s.
Reaching with his hands to grab the older’s face, Ichigo locked eyes with the Arrancar, determination shining in the amber orbs ‘’Okay, but I don’t want to eat human souls, and I want you to hunt with me, I’ll feel better if you’re at my side’’
Grimmjow let out a mix between a trill and a meow at that and jumped to his feet, taking the ginger with him.
‘’ Hell yes!’’ the smile on the Arrancar’s face was blinding, showing off his fangs that gleamed under the moonlight. Ichigo’s heart skipped a beat. Or two.
Taking Pantera back from the ground, Grimmjow unsheated the blade and let out a playful growl ‘’ Since yer gonna need yer Vasto Lorde form fer that Imma go into Ressureccion. I don’t need ta eat so I’ll only help ya hunt and enjoy the show’’ with a suggestive smirk and a wink, he unsealed his powers.
Red faced, Ichigo growled at the other before picking up his blades and shifting, ignoring the surge of reiatsu from Grimmjow’s release. Zangetsu joined into his first bankai form as it always was in this form, pitch black with the chain at the end of the guard.
The familiar weight of his mask reassured him as his hole opened and his clothes shifted. Fur and claw sprouting from his hierro as it extended along his body numbing the sensation of the wind on his skin and his hair caressing his back. The prickling in his eyes told him they were now gold on black, wild looking and unrelenting. He felt better already.
Adrenalin pumped in his veins and he let out a triumphant roar, the power coursing through him asking him to tell the world of his superiority. He was followed by the answering one of Grimmjow, like a call to the hollows prowling the sand of the two predators coming for them ( hunt, hunt, hunt ).
They crouched as the roars died down, facing the moon and looking out at the beauty of Hueco Mundo’s sand. Grimmjow tapped Ichigo on the shoulder with his tail to indicate he would go first and disappeared in a burst of Sonido. The ginger didn’t waste any second to follow his mate’s scent towards what felt like a pack of weak prey.
The hybrid’s mouth watered at the scents, some more appealing than other. He quickly found out the stronger ones smelled the best as Grimmjow took to the left to herd three Adjuchas class hollow to his mate.
The ginger let his reiatsu flow out as the prey tried to flee but they were so weak they got flattened the moment Ichigo’s power hit them. Following his instincts, the Vasto Lorde grabbed the strongest by the neck to eat first with a threatening growl that seems to vibrate across his hollow hole.
In a last ditch effort the prey lashed out and tried to hit Ichigo but the ginger dodged the weak attempt and opened his mouth to absorb it’s reiatsu. He knew he could eat the flesh but didn’t feel ready to do that with sentient hollow like these ones.
The feeling of fullness that came was so good Ichigo wondered if he would ever stop. It was addictive, having that emptiness filled after so long, he hadn’t realise he was starving. He couldn’t make himself feel guilt if he tried as he ate the last one and a low croon crept out of him.
A trill made him look to the side to see Grimmjow radiating pride beside him. The sight sparked something in Ichigo and the next second he was on his mate, the older male sprawled on the sand with a lap of Vasto Lorde.
Ichigo crooned ( play, play, I want to play )
Without waiting for an answer the ginger jumped out of the other’s lap and crouched in the sand, his eyes fixed on his mate.
Grimmjow laughed before growling playfully ( run, run, run so I can chase ) and jumped on the ginger.
He ended up in the sand on all four, Ichigo meters away, taunting him with trills and croons.
‘’ Oh yer on Ichi’’ Grimmjow said before starting the chase.
They spent hour chasing each other, rolling in the sand dunes, laughing as they ran and toppled the other all over Hueco Mundo. At one point, the building energy was too much and they started fighting like always. They ended up sprawled in the sand, bloody and battered, laughing like crazy. They were both back to normal.
‘’ If yer gonna be like that each time ya hunt ya need to tell yer pack so they don’t worry. I ain’t complaining mind ya, t’was a damn good fight’’ the Arrancar said breathlessly. He couldn’t move if he tried, he was completely spent, even his mask fragment hurt.
Ichigo laughed at that before wincing as one of his cracked ribs moved wrong at the movement ‘’ Yeah, I don’t know what came over me but it was a blast, I don’t think I can even use my regeneration, that’s how much I’m spent’’
A pleased chirp came out of Grimmjow’s general direction ‘’ Damn right ya can't, yer not the only one getting stronger as we fight, I’ll never go easy on ya, Kurosaki’’ then he smirked and added ‘’There’s always another way of letting off steam for next time if ya don’t want to explain to yer pack why yer all bloody and bruised ya know’’ if he had the strength, he would have wiggled his eyebrows suggestively even if Kurosaki couldn’t see it.
Ichigo’s face burned and he sputtered, half from embarrassment, half from the pain ‘’ Grimmjow!’’
‘’ What’s the matter, Kurosaki. Ya don’t wanna get dirty with me? I’ll say it’s too late fer that’’ the Arrancar tried for humour but he was glad the other couldn’t see him because he couldn’t mask the worry from his face and he didn’t want to think of the ginger rejecting him.
The hybrid could hear the hesitation in his mate’s voice however and beat down his blush to reassure him ‘’ That’s not it, you’re my mate, of course I want to do that with you one day! But I can’t kiss you with the mask on my face and I don’t want that.’’ he really couldn’t imagine doing anything with that hollow mouth that could bring pleasure in any form. It wasn’t like Grimmjow’s fangs, his teeth when he donned the mask were vicious, made for tearing flesh appart, not tender love bites.
The Arrancar let out a trill of joy at being called the ginger's mate. Him, it was him that this powerful creature had chosen as a mate and he was ecstatic, he wanted to show it to the world but he still couldn’t move so he basked in the knowledge instead.
‘’ We’ll have ta make an Arrancar outta ya then, so yer mask’s not in the way anymore’’
‘’ You think that’s possible for me? Are Arrancar even naturally born in Hueco Mundo?’’ Ichigo learned more about hollow every day but he still lacked inherent knowledge that he knew came with living in this realm for years and consuming other hollows.
‘’ They can, it’s just so rare nobody thought they were a thing before the bastard Aizen came with his fuckin’ marble and made us. The Primera was a natural Arrancar. As for ya, yer a Vasto Lorde and those are plenty rare enough I’ll say there’s no way you can’t evolve further’’ at the rate Kurosaki was going with all his power, he’ll probably be one in less than a year, he could wait that long. ‘’ Yer probably gonna need to hunt more for that, but the gist is that Arrancar are just hollow that ripped of their mask and survived.’’
Ichigo knew that last part, and that was what made him sceptical. He was a Visored and could just put his mask on and off. But he also was the only one with a full hollow form so he probably could take it off the hollow way and evolve. He would just need a strong motivation.
Turning his head slowly towards Grimmjow despite the pain, Ichigo thought about his mate’s gorgeous body under him and smiled.
He had a damn good motivation.