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Katsuki has made his peace with being a beta.
It’s antithetical to his whole vibe and he’s extremely aware of that. Everyone he’s ever met has had something surprised or snide to say about it, which quite frankly pisses him the hell off. But what is he supposed to do about it?
Disagree? No. What’s the point in that?
They’re right, whatever damn way you look at it.
He should be an alpha. His mom is, and he’s a matrilineal carbon copy of her down to his bones. Every single one of his personality traits and overall characteristics indicate that he should be, even if that’s wildly stereotypical to assume. Both of his parents expected him to be one and his mom still holds out that he’s just a late bloomer, but graduating high school and still not having presented feels like a pipe dream.
He’s a beta and that’s all there is to it.
Sometimes he wishes he was an alpha, but that’s happened less with age and maturity gained via trial by fire.
He is what he is, in almost every way. He’s getting better all of the time, but at his core, he’s relatively consistent. Beta or not.
Shouto, on the other hand, both is exactly what and who he’s expected to be and also the exact opposite at almost all times.
One of the most powerful people he’s ever met, quirk and all. Comparable to Katsuki in terms of booksmarts, but an actual literal idiot in every other context. Socially stunted but occasionally so earnest and blunt with his feelings that it cancels out. And an omega, to top it all off.
He smells sweet, fresh. Like the first breath of cold air on a snowy day layered underneath a smoky sort of warmth. Overkill, with his whole deal, but nice enough all the same. Katsuki can smell him better than most people and he doesn’t even really mind it.
Most of the time, he figures the awareness of how Shouto smells compared to the general people-scent of most of the extras he engages with is probably because of his stupid fucking Shouto thing in the first place.
He’s compelling and unfortunately interesting and mostly wildly fucking stupid. But Katsuki noticed him from the start, from that very first meeting. And has kept noticing.
Which is how they’ve ended up here, Shouto rolled up underneath him, nestled in his bed with all of the extra bullshit bedding he always needs tucked up around them both, smelling like a blown out candle overtop of crisp, freshly fallen snow. It’s the second to last week of their high school careers and Katsuki is giving in to something that’s felt inevitable since the moment he met Shouto.
This being where they’ve ended up shouldn’t be surprising.
Katsuki has always been weird about him, unfortunately entranced by all of Shouto’s fucked up vibes. Initially like a car crash where he couldn’t look away, then more so where he turned to Shouto to look at him. On purpose. Ugh.
And Shouto was so goddamn persistent about being friends that it felt inevitable anyway. Plus, he smells so fucking good that it’s actively annoying.
They’ve been fooling around for a while. Ostensibly in a friends-with-benefits way at first, to get all of their late teenage angst and persistent drive out on someone who could handle it, now more so in a hey-we-should-probably-live-together-after-graduation way. As they figure out their careers and their futures or whatever. And to save money, of course.
In a mutually exclusive non-determined feelings based relationship way, because neither of them have two brain cells to rub together in the context of communicating their feelings appropriately between them.
And Shouto has said multiple times that he doesn’t mind that Katsuki is a beta. Which of course makes Katsuki start yelling about hell yeah he shouldn’t mind, there’s nothing to mind, his dick still works and is a very normal if not above average size, thank you very fucking much! that did very little to dissuade Shouto from reassuring him again the next time he noticed Katsuki was being weird about it.
Nice, but not fucking necessary.
Like most things about Shouto, honestly.
All of this to say they’re extremely compatible on a variety of levels, not just quirk-wise. They work and it’s pretty easy to be around him. Even easier to be on top of him.
Katsuki knows Shouto isn’t a virgin, judging almost exclusively by the way he sucks dick. But he’s not going to do something fucking casual like ask about his previous hook ups. Katsuki isn’t new to this either.
He is new to specifically this with Shouto, though. They haven’t fucked before, not for real. And it’s inevitable, so now they’re here, pressed together shoulders to hips in Katsuki’s bed.
The sweat dripping down his back prickles as he shifts onto his elbows to look down at Shouto beneath him. Half-and-half hair pushed back, sweaty at his temples, he looks like a fuckin’ dream. And his eyes are fucking huge in his face where he looks up at Katsuki.
Shouto looks drunk, kind of. Pink cheeked and big-eyed and dazed. Lips kissed shiny and swollen. Katsuki can’t help but duck down and smush his face into Shouto’s neck, where he smells best. Deep, rasping inhales right against his scent gland are the only thing that makes Katsuki feel like his head is still on straight.
Shouto is wet between his legs, too. Katsuki doesn’t need to be an alpha to smell that.
He spent quite a bit of time down there earlier, pushing his tongue up into Shouto’s cunt. Then around his clit, with a few of his fingers slipped in, Shouto making soft, cut off gasping noises as he rocked down, mumbling about how calloused Katsuki’s fingertips were.
It’s good. This part of it has always been good, messing around with fingers and tongues, grinding on each other until they’re desperate with it.
Katsuki is pretty sure this next part is going to be better though.
It’s not much work to slick up his dick with everything Shouto is leaking, mixed with his own spit. His heartbeat is pounding in his skull, but he’s pretty sure that’s just because he’s excited and because it’s kind of hot in his room, not ‘cause he’s nervous or anything like that.
They’re fucking raw because Shouto is self-admittedly on the best kind of birth control money can buy and because even the mere thought of fucking with a condom and not being able to feel Katsuki the first time made Shouto whine so loud Katsuki thought he was legitimately in pain.
Underneath him, Shouto is purring loud as fuck, throwing off enough pleased, fuck-me pheromones that it would probably make someone lesser than Katsuki pass the hell out. He isn’t particularly attuned to most pheromones, what with the beta thing, but he can clock them from Shouto. Even more so with how he keeps arching up to layer wet, open mouthed kisses against Katsuki’s lips like a goddamn siren.
Sliding into him is easy. He wouldn’t say something cringey about how it’s like coming home, but it’s pretty fucking close. Shouto is tight and wet around him, clutching at him, mumbling little pleas and bitten-off moans of Katsuki’s name.
It’s a lot.
Katsuki is sweating more than he typically does, but one of Shouto’s hands dug into his shoulderblades is actively hot to the touch. He tries to focus on the cool relief of his opposite hand, but gets a little bit distracted by how aware of his teeth he suddenly is.
They kind of—hurt. A little. In the front, not in the back where they usually ache when he grinds or clenches them.
Shouto cants his hips up and slides his cold hand into Katsuki’s hair and suddenly his teeth are the least of his problems.
He rolls through a few tiny thrusts, checks to make sure that Shouto isn’t in any pain and is also still breathing—which he soundly is, great gasping breaths that stretch out his toned chest and draw Katsuki’s attention to his nipples—then gives it a little more effort.
It’s fucking good, but of course it is, it’s he and Shouto. Them coming in their pants after grinding against each other while making out for hours was good. This is even better.
With each increasingly intense thrust, Shouto makes a little punched out uh noise and Katsuki is so hard his dick actually hurts.
He really can feel his heartbeat in his ears, he thinks. His heart rate right now can’t be healthy, but he’s too focused on fucking his pseudo-boyfriend up the mattress to really worry about it.
Something might be wrong with him, physically. But he’s so horny he can’t really think straight. Especially when Shouto uses the hand in his hair to wrench him down toward him so they can pant into each other’s open mouths.
Shouto is meeting each of his movements with his own, rolling his hips up fluidly. Scratching his hot hand down Katsuki’s back, he hikes one of his legs higher up Katsuki’s hip until he’s got no choice but to hook it under his elbow, spreading Shouto wide.
He groans, loud and gorgeous, and tosses his head back. The motion reveals his throat, exposing his scent glands and sending that delicious icy smoke smell right into Katsuki’s entire brain. The deep rumbling inhale he takes in ends with a sound coming out of his mouth that surprises even him, even though he’s the one it came out of.
Hurt, but still pleased. A kind of surprised pleasure-pain.
Still spread out beneath him, Shouto makes a confused sort of crooning sound. Slipping both of his hands onto Katsuki’s face, he steadies him, makes way too intense eye contact with his cat-like eyes. “You alright?” he asks, his typically steady voice tilting up at the end when Katsuki continues to fuck him.
“Never been better,” he mumbles back, somewhat slurred. His teeth feel like they don’t fit into his mouth, but his impending orgasm feels white hot in his belly and he wants to get Shouto there first. Because he’s a gentleman, goddamnit.
The arm with Shouto’s knee hooked over it is planted on the bed to brace Katsuki over him, and he shuffles a hand down between them to swirl his thumb over the hard bud of Shouto’s clit. He’s slick all the way down his inner thighs, the both of them messy with it.
Katsuki can admit he did a lot of research over the last few years on the safety concerns of nitroglycerin and him putting parts of his body in other people’s bodies. But he’s relatively confident now that sticking his fingers in Shouto’s mouth to have him lick the slick off them won’t do anything to Shouto aside from maybe give him lower blood pressure.
Not that he needs that, but still.
He wants that now, wants it so bad it feels like a pulse behind his eyes. He wants Shouto to come, to tighten up on his cock, to get his fingers all slick and wet. Then he wants to brush them across Shouto’s stupid perfect mouth. Have him lick them clean.
Then he wants to fit his teeth to the arching slope of Shouto’s neck. And bite down. Hard.
After that, he wants Shouto to bite him back. Wants to feel the sharp prickle of his ridiculous needle-like omega teeth. He wants it so fucking bad.
Shouto is twitching beneath him, his overwarm fingers circled like a brand around Katsuki's wrist where it's tucked between his thighs. He’s close, Katsuki can tell by how he’s moaning, by the rhythmic clenching of him.
The little voice inside of him that he’s always been pretty sure is his conscience but is particularly loud right now keeps chanting that he needs to get Shouto there first, needs to get his omega off before he can come, because that’s how it needs to be. How it has to be, every time.
He’ll do it, he swears. His knees kind of hurt and he’s out of breath and his fucking teeth ache but he’ll do it.
Shouto is mewling under him, groaning his name. The hand not around his wrist comes up to swipe low under Katsuki’s right ear, where his particularly inactive scent glands are. It feels so fucking good that he almost comes at the touch, a pathetic whine spilling out of his mouth into Shouto’s.
What the fuck is going on?
“Mine,” Shouto whispers, forceful and intense and claiming. “You’re mine, Katsuki, mine.”
He presses down harder on Katsuki’s suddenly sensitive scent glands and Katsuki can’t stop it, no matter how hard he tries, no matter how badly he doesn’t want to come yet, wants to get Shouto there first—
Everything hurts for a split second, a terrible, awful burst of pain stemming from his teeth and ricocheting out into his body to settle, regrettably, into his still-hard dick. His vision goes black, then fractalizes into a burst of shimmery white crystals and suddenly everything is so good, so perfect—
He comes back into his body with his cock shoved so far into Shouto that he’s shuffled him even further forward up the bed, bent in half, Shouto’s knees almost to his shoulders.
And Jesus fuckin’ Christ, something is wrong with his dick. He’s still coming actually, even after the black-out-white-out franticness of his orgasm. Unconsciously, he grinds even further into Shouto and groans with how good it feels.
Shouto makes an inquisitive, confused little sound in the back of his throat, then his entire body shudders violently in an outward ripple and he comes so hard his eyes roll back into his head.
What the actual literal fuck?
He’s still twitching and groaning as Katsuki shuffles off of him a bit, flopping his legs back around his waist instead of up by his ears.
“What the hell?” he asks both to himself and to Shouto, who is so out of it he can’t be assed to even acknowledge that something is very much wrong with Katsuki right now.
Continuing to edge down the bed, he gets his knees back under him and glances down the length of he and Shouto’s bodies to where they’re connected.
And fuck, are they connected.
At the base of his dick, which typically looks normal as fuck and not at all like it does right now, is an odd, thick ridge just barely visibly from where it’s plugging Shouto up.
And Jesus, he’s obscenely stretched around it. Normally Katsuki’s fine with what he’s packing, but this is like, egregious. No wonder Shouto came just from Katsuki popping a knot.
It’s a knot. Katsuki’s got a fucking knot.
Fuckin’ hell.
He tentatively tries to pull out, just a small movement away from the heat of Shouto’s body. It tugs at them both, making Shouto whine and flop a hand onto his back. But his cock doesn’t move, doesn’t even budge.
Holy fuck. Katsuki has a knot. Katsuki’s a fucking alpha.
No wonder his teeth hurt, he thinks absently, tonguing along them. The tips of his canines feel significantly sharper than they did an hour ago.
Desperately, achingly, he still wants to fit them to the slope of Shouto’s neck.
All of the blood rushing to his dick and the fact that he’s pretty sure he’s still coming into Shouto right now is enough to get him to tip forward without thinking. Nosing at Shouto’s neck, he takes another deep inhale, Shouto’s scent so good it feels like he’s hearing colors.
Easy, like it costs him nothing, Shouto turns his head and bares his neck with a soft little noise and a pointed clench around Katsuki’s cock.
If he hadn’t been knotted inside of him, that would’ve been enough.
Slowly, carefully, he layers a few kisses on Shouto’s scent glands. Then, because he’s a dirty, highly motivated bastard, he licks a fat, wet stripe up the side of Shouto’s neck.
The touch has Shouto moaning, grinding up into his knot. The pretty splintering crystals shower back down over Katsuki’s vision. Fuck, that’s so awesome.
He opens his mouth, because he can’t help it, and gently circles his teeth around Shouto’s scent gland. It tastes so good, earthy and innate, like the heat of blood in his mouth and the essence of everything that Shouto is. Smoke and the sweetness of his slick.
The pressure around his scent glands has Shouto arching up into him, moaning sweet as fuck. His pretty deep voice curls around the syllables of “alpha” so nicely that Katsuki can’t help but thrust into him again.
They’re both making ridiculous, slightly animalistic noises. He’s pretty sure Shouto is going to come again, what with the shallow grinding movements they’re making against each other. He’s so deep inside of him, something Shouto keeps quietly murmuring about into Katsuki’s right ear.
His alpha, because that’s what that voice fucking is, what it might always have been, is crooning about making his omega come again. And who is he to deny what his apparently true self wants?
Fuck, Shouto is his omega. He was before, when Katsuki thought he was a beta. But he really fucking is now.
Katsuki can claim him, once they get settled into their hero careers, after they secure an apartment and jobs and maybe a cat or two between them. Katsuki can claim him and Shouto can claim him back and his dick is still so ridiculously hard inside of Shouto he’s surprised he’s still conscious.
Everything has changed in the last twenty minutes.
Everything has changed because he got Todoroki fucking Shouto under him, got in him, and something about the insane effect they have on each other caused him to present later than anyone he’s ever known.
Fuck. His mom was right. Goddamnit it.
Quietly, sweetly, Shouto tilts his head again and asks, “Will you put your mouth there again?” and then groans when Katsuki immediately presses his teeth to his scent gland they’re magnetized there.
He groans even louder when Katsuki slips his hand between his thighs again, thumbing at his clit.
There’s going to be a lot for him, for them, to explore with this newfound, fucking world changing alpha-relevation. A lot to learn. A lot to get really, really fucking good at. Including fucking his perfect, ridiculous, idiot omega stupid.
Katsuki is going to be the best goddamn alpha of all time. The best alpha to Shouto.
When he speaks through his teeth, jaw still held tight against the pulse of Shouto’s scent gland, and tells Shouto as much, he moans loud as fuck and comes all over the both of them again.
Good thing they have nothing but time.