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Grimmjow is a wild animal.
An apex predator right down to the very center of his soul. Brutal and solitary. Forged in blood and strife. Stalking the afterlife with practiced, silent steps. Reigning death down upon any being unfortunate enough to land itself in his sights. Cruelty and violence given form.
The Substitute Shinigami he has chosen as his object of obsession is… not that. Grimmjow knows Kurosaki has it in him– that bloodlust that he works tirelessly to tease out when they tear each other to shreds in Urahara’s underground bunker every week or so. (It had taken over half a year of hounding to get the Shinigami to agree, and another handful of months to convince him to actually give it his all). But while Kurosaki’s soul echoes with the same ferocity that rivals Grimmjow’s own, the whole of him is soft. Warm. Blistering sunlight that Grimmjow holds between his teeth, threatening to ignite something within him.
And he knows that if swallows it down, it’ll burn him to his core.
It starts simple. Slow enough that Grimmjow doesn’t even realize it’s happening.
The two of them are sprawled out, breaths ragged and skin bloodied from their most recent bout. Grimmjow moves to get up and claw his way back to Hueco Mundo to heal under the watchful eye of the lonely moon like he always does. Only, his legs aren’t working right and he’s pretty sure his half-shattered spine is the culprit.
Kurosaki is limping badly, but he gently wraps the arm that isn't dislocated around Grimmjow’s torso and, leaning heavily into each other, begins drag-carrying them both towards one of the far walls of the training grounds. Grimmjow bites back a sound as the movement jars something terribly in his ruined back despite the care being taken, and Kurosaki looks at him with awful concern. “This'll help. Just give it a minute.” is all Kurosaki says, depositing him into the hot springs before he can protest. Kurosaki lowers himself in on the other side of the rock pool, keeping a respectful distance as the warm water washes away their injuries.
Grimmjow knows Kurosaki could have just as easily called his busty friend over to patch himself up like he’s done before. She’s offered to heal up Grimmjow too, on the rare occasions that he needed a moment before scurrying away to recover alone, and he always refused. As much as he could begrudgingly respect her abilities, the feeling of her sickly-sweet energy– bubbly, sparkling, nauseating– tracing along the contours of his spirit made his skin crawl. He’d had enough people messing around inside his soul when Aizen left his mark.
Kurosaki had noticed. Grimmjow realizes, staring up at the fake sky and bristling only a little bit at the memories of the the last time he had been made to live under false sunlight. Kurosaki had noticed and remembered. Opted for the slower recovery of the kido-enchanted springs for both of them because he knew Grimmjow would rather lose his left arm again than be treated differently. Called out on his discomfort.
(He wouldn't be surprised if Kurosaki still went to her afterwards to fully fix the damage wrought upon his rotator cuff.)
It's strange, being so close to Kurosaki outside of battle. An upset of the usual. But Grimmjow can't deny that it beats gritting his teeth through the pain as his bones knit themselves together on their own. Relaxing into the silent warmth, he swears to himself that he’s not going to make a habit of it.
He follows Kurosaki to the pool after their next fight anyway.
It becomes A Thing. And Grimmjow doesn’t look too closely at it. Doesn’t draw attention to the change in routine. It’s just healing after a battle. That’s all.
They talk. Or at least, Kurosaki talks and Grimmjow does his best to radiate disinterest. He has no interest in meaningless human frivolities like school and work and family, but receives dutiful reports and weekly updates anyway.
Sometimes Kurosaki asks questions.
Sometimes Grimmjow even answers them, giving up tidbits of his guarded self that he can afford to lose: what is it like living in Las Noches (stifling), how is Hueco Mudo now that the Quincies are gone (boring), does he know what Nel and Harribel have been up to (hell no).
The inquiries are never prying– Kurosaki expertly steers away from topics that Grimmjow would bite his head off for daring to touch– and always tinted with genuine curiosity. As if the hybrid soul that shook the very foundation of the four realms actually cares. As if they were friends instead of rivals who have decided– for some ridiculous, unfathomable reason– to not actually kill each other like they should. And Grimmjow hates himself a little more whenever he doesn’t manage to keep his stupid mouth shut. Because the reality is that it's easy– too easy– to let his guard slip like this.
Despite it all, he finds himself delaying his departure more and more each time, making half-baked excuses to linger. Putting up with the infuriating inhabitants of the shop just to have one more second of those maddening eyes on him.
He can feel the gravitational force pulling him into Kurosaki's orbit. A dizzying whirlwind of golden sparks, flashes of teeth, and something Grimmjow can’t name, writhing in the space where his heart should be; some part of his mind and body outside of his control.
Intoxicating– addicting– are the words his mind finally settles on, because if hollows could get drunk, certainly that is what it would feel like. And because in spite of how it makes him feel stupid and slow, he wants more.
Grimmjow runs, spooked. Hides away in the sands to quit cold turkey before it’s too late. A week goes by where he doesn’t show up for their usual fight. Then another. But he's always been honest with himself to a fault, and has never been good at denying himself his desires. He needs those fights. He needs Kurosaki, fired up and out for blood and looking at him like nothing else matters. Whatever follows is… fine. It's fine.
He doesn’t make it a third week.
Kurosaki greets him like he never left.
Even with their strangely evolving dynamic, they still battle with the same ferocity; a refreshing reminder to Grimmjow of what they are both capable of when they’re not pretending to be anything other than the monsters they truly are. The bloodshed clears his mind, pain focusing his world back into a familiar kaleidoscope of sharp angles and jagged, red shapes. Kurosaki’s left eye is hollow-black as Grimmjow braces against the liquid fire of a cero that rattles the whole foundation. And for an hour. Two. Four. However long they go at it, the world is made simple again.
But there is always the after. The slow come-down from the high. The unspoken routine they have settled into: Fight. Hot springs. Lay around in the bunker or in Urahara’s back room until either Grimmjow gets restless and tears his way back into the silence of the empty world, or until Kurosaki decides he has procrastinated on homework long enough and heads back home.
Grimmjow doesn’t even remember the first time he followed Kurosaki back to the stupid little one-bedroom flat on the outskirts of town. He doesn’t know when Kurosaki started leaving out a spare blanket on his old, beat-up couch “just in case”. As if Grimmjow would be enticed to hang around for longer. As if a nighttime chill was something he would be even remotely concerned with if he did decide to stay.
The blanket goes unused until it doesn’t.
Kurosaki is endlessly patient with him, riding the waves of a hollow’s fickle, stunted emotions with a grace that Grimmjow knows he doesn’t deserve: trading playful insults like a second language when he needles him for fun, giving space when all of the feeling becomes too exhausting, hitting hard when he needs blood and violence to ground himself.
It’s almost too much, the way the Shinigami is tangling into his life, entwining them together in a way that he knows will make it impossible to extricate himself from. But they’ve been like that since their very first meeting, haven't they? The scar along Grimmjow’s chest tingles with the memory of scorched moonlight. He had been the one to bind their souls together by keeping the mark, wanting– needing– to be close to that cold fire.
(There’s some terrible thought, buried so deep in the back of his mind that he doesn’t even dare to look at: if Kurosaki was hollow enough to ask to devour him, he wouldn’t be able to say no.)
Urahara gifts him a gigai with a sly, conspiratorial wink, kitted out specifically for a hollow of his calibre. He tries it once. Twice. Chafing against the restrictions of the fake body. He feels stupid walking, existing, living. Or at least pretending to. He hates it. But Kurosaki smiles bright when he enters the shop and sees him dressed casually and missing the familiar mask fragment on his cheek, takes his hand– the feeling electric compared to everything else so far away and muted through the false skin– and leads him to a quiet cafe a few streets over. Somewhere, distantly, he remembers that he liked the taste of black coffee.
Kurosaki continues infecting his life, little by little. Small smiles that Grimmjow has never seen shared with anyone else, laughter that rings like music in his ears long after its source has quieted, a hand placed on his soulder– not to scratch or maim, just there. And it should make him angry, fearful, defensive, but he can’t muster up the energy to shrug off the touch.
Each advance is only a tiny step forward, so gradual that Grimmjow is in over his head before he realizes there's no ground beneath him.
The gigai gets more use, Kurosaki dragging him to places he has absolutely no right being: a beach covered in glittering shells. A wooded trail up a mist-covered mountain. A festival overflowing with lights and sound and smells so overwhelming it wrinkles Grimmjow’s nose. And he… he shouldn’t be there. He can’t even remember the last time he had an actual heart beating in his chest, and if any of the unwitting humans around him had even a spark of reiatsu worth his notice, he surely would swallow them whole. Still, Kurosaki brings him along and curates little moments that Grimmjow doesn’t know how to categorize.
(To make it fair, Kurosaki allows himself to be badgered into joining Grimmjow on a proper hunt in the lonely desert; ends the day bloody and breathless and absolutely beaming.)
The realization hits him on a random day in autumn, sharing the lumpy second-hand couch with Kurosaki– their legs tangled together as they sit on opposing ends of the sofa. Grimmjow watches the gentle rise and fall of Kurosaki’s chest, the book he had been reading perched precariously on his lap as he sleeps. Grimmjow’s eyes trail up the Shinigami’s human form, settling on the bare skin of his neck; the steady pulse of Kurosaki’s heart thrumming just beneath the surface.
He stands with the silent, practiced grace; looms over the sleeping form of his rival-tuned-whatever-they-are-now. He can’t comprehend why Kurosaki still insists on playing at being human, especially given all the time he spends ejected from his own body anyway. But here he is. Weak. Exposed. Vulnerable. Fragile.
It would be nothing to reach down and wrap a hand around that throat. Squeeze until Kurosaki’s pathetic life sputters out like a dying ember. Easy, even, instincts already calculating pressure and force.
But for the first time in his entire afterlife, Grimmjow doesn’t feel the impulse to extinguish that flame. He reaches down and moves the book to the end table before it has the chance to fall. Kurosaki’s eyes don’t even flutter.
And there, surrounded by soft domestic warmth unknown to him before Kurosaki, Grimmjow wonders how he allowed himself to be tamed.