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“K-Kacchan,” Izuku says, eyes hauntingly wide as his lips part and Katsuki leans in to steal a brief kiss so he doesn’t have to look at them too long. Those large eyes always fucking him over, calling to him like a siren’s song and Katsuki is always three step from jumping overboard.
Katsuki’s lips trail past Izuku’s cheek and down his jawline until he comes toward his destination. He presses his nose up against Izuku’s bare neck as his teeth throbs, lips parch with hunger and want, and every stretch of his skin feels like it’s on fire, but he doesn’t bite down. He can’t. Not yet.
“Let me,” Katsuki begs, voice pitch low as he hunches over Izuku’s prone form on the bed. Let me have you, he didn’t say but it’s in the tense lines of his body and the pain in his voice, how Katsuki hurts all over to have him.
Katsuki lets out a trembling breath as he will himself to draw back even though the urge to bite down on the bare flesh, to leave a mark so deep that Izuku will feel it down to the marrow of his bones, is so tempting.
Izuku’s eyes are wet now as he fights back tears, his lips wobbling and Katsuki is so incredibly fucked.
Everything about Izuku’s presses his button from his smile, to his eyes, and to his very existence but his tears, they wreck Katsuki like nothing else because Izuku is always finding an excuse to cry and it makes something of a monster in Katsuki. He hates it, absolutely loathes every second of it because then he wants to hunt down and end the source of Izuku’s tears, to mend whatever hurt him, and to tuck him away somewhere safe and quiet so Katsuki can protect him against the world and everything in it. It takes every drop of his willpower and training to not answer that call, to give in to the lizard part of his brain that just want to roll over and please his omega but always, always in the back of his mind it’s a trigger waiting to be pull.
Katsuki leans in and licks a stray tear that escape, tasting the salt and Izuku on his tongue. “Shh, shh, don’t cry,” he soothes, trying to fix a crack dam with bandage tapes. “I’m sorry so don’t cry. I won’t do it if you don’t want me to.” It hurts to say it, but he will. Katsuki can go up against All Might with nothing but his bare fist but a single word from Izuku can undo him. It’s a frightening thing.
Izuku shakes his head. His eyes are still wet but he smiles big and wide as looks up at Katsuki with utter adoration in them. “I always want you Kacchan,” he says, like a bullet to the heart.
Katsuki’s weakness has always existed in Izuku since they were children and Izuku had dug into his chest and pried out his heart. Izuku has always kept a piece of Katsuki close to him since then, even when Katsuki had pushed him away and had punished him for being the sole keeper of Katsuki’s fault, for being the one thing Katsuki will destroy himself over and over again for.
So Katsuki needs to hear it, need to have Izuku verbalize it and cemented because if he’s going to kill himself over it he like for Izuku to say those damning words. “So tell me then,” he says, the words coming fast and unbidden. “Tell me I can do this, tell me you want this, tell me and I’ll lay the world at your feet.”
Izuku’s cheeks stained a pretty pink and Katsuki presses a gentle kiss there. “Tell me what you want, sweetheart,” he says.
“Kacchan, I want you to mark me,” Izuku finally lets out, and the words are all Katsuki need. “Please.”
Katsuki grins, proud and revitalized as he presses his face in close once more. “Thank fuck, I thought I was going to die,” he says and Izuku laughs, bright and happy and it warms Katsuki all over.
He traces the fading bite mark, teeth scraping the tender flesh and tongue teasing the site that he'd marked before. “Kacchan, please,” Izuku says and this time there’s an urgency and need in it that compels Katsuki forward to seal the deal. He bites down hard, till he can taste the metal tang on his tongue and Izuku's blood is his absolution.
He pulls back reluctantly, seeing the indentation of his teeth and redness breaking through the skin. “Don’t forget,” Katsuki says, staring down at Izuku’s flushed face and wet eyes. It’s a threat and a promise all at once.
Izuku smiles, soft and sweet so full of love that Katsuki can’t stand to look at it, wants to hide from it. “You’re mine and I’m yours, I know.”
With that, Katsuki collapses on the other side of Izuku and just for a couple more minutes they’ll have this, just breathing each other in and this bond that marks them as something more.
It’s a ritual at this point, what they are doing.
Outside of this room, this sanctuary of theirs is a world that tells them what they are to each other--movies, TV, books, and everyone who got a fucking opinion on it but had no business in it. They will tell him how alphas are big and strong and that omegas are wilted flowers and need to be handled with care but they never face up against Izuku and never feel the utter sense of helpless under Izuku’s tears. They never tell him what it’s like to be consumed by this feeling, to be wrapped under Izuku’s spell.
The media and everybody else are quite frankly fucking horseshit. They don’t know anything at all.
To the world, they were childhood friends once and now they’re rivals, vying for the number one hero spot. It’s an aged old story: there’s a shared history between them that is a layer with guilt, hurt, and anger and is now complicated now by their secondary sex, an omega versus an alpha but that’s no contest.
Katsuki shouldn’t be held accountable to Izuku, he can’t be bending himself backward for an omega but he is and he does.
Because sometimes, sometimes when the call of Izuku’s scent gets too strong, Katsuki’s fine tune control get completely shatter like the most fragile of glass under the ruthless onslaught of Izuku’s pheromones. He’ll come crawling to Izuku’s door half mad with a fever that only Izuku can cure and Izuku will be waiting for him. He’ll corner Izuku in the bed and rip off the choker that Izuku always wears around his neck as a sign of an unclaimed omega and then he’ll ask and plead for a chance to mark Izuku up again, to reclaim the boy who owns him inside and out since they were dumb children, who didn’t understand the consequence of their action.
Once they’re done, Izuku will put his choker back on again, hiding the bite mark once more before they part way, never mentioning what transpires between them. They will go on their days in a different circle of friends, training to be number one, and fighting villains. They will cross path as to be expected because they can never be too far apart for along and to everyone else, they will be none the wiser because there’s nothing to show for it.
But when next week comes around they’ll do this all over again. This is his and Izuku’s secret.
Out there in the world, Katsuki walks with a confident stride, unrivaled and untouchable but here in this small space shared between them Izuku’s words are his benediction and his tears are his downfall and that’s the truth Katsuki can’t hide.