All it took was one unfamiliar scent to set him off.

It didn’t happen often, because all of the UA student body knew. An unwritten law of the school: who Kirishima Eijirou belong to.

It had taken some time. Quite a bit of posturing. Nights where his teeth did nothing but ache for hours upon hours; for how long he’d been grinding them over. Pushing out his fangs.

But hitting third-year, school extras finally learned and submitted - backing the fuck off.

Now, if only the rest of Japan would get the fucking memo.

There’s only so far his alpha stench can reach. A pair of bared fangs only looked so menacing from afar. Only so many peopl in Eijirou’s world could know Katsuki existed.

Not everyone realized they were saving their mating bites for when he and Eijirou struck pros.

It’s always because Eijirou is perfect. Eijirou is patient. Even the tiniest hair-brain would see what an amazing partner he made.

...and that’s usually what would set his alpha off.

Because there’s only one alpha perfect for him.

Katsuki never failed to remind him of it.

Even if it meant showing off in front of all of their friends.

Eijirou knows better than to come back into their den smelling like weak, little dick alphas.

“Oi.” He grouses, making his way to the couch his omega all but threw himself down on.

A second ago it had been coming to talk food and maybe a little palm scenting. Trying to coax him upstairs and away from all the extras.

Gone for a week. Here for five minutes. Eijirou probably missed them all; Katsuki knows Ei’s social by nature. But he also knows there’s a nest upstairs in need of repairs and lots of scents - definitely cum.

Of course, everything freezes as soon as he smells foreign alpha saturated over tanned skin.

Suddenly it’s not about the welcome back he’d planned.

It’s destroying the competition.

Eijirou’s chin tilts up as soon as he approaches.

Katsuki immediately takes stance.

“Omega.” He growls, tasting the way it leaves his lips with a slow lick.

Looking deeply into wide eyes, only Katsuki sees the way those pupils blow up almost immediately.

It’s like a siren’s call through the waters. Snaring every sailor hopelessly into her trap.

Katsuki may be hopeless when it comes to Eijirou. Being the only one wanting his attention on.

But Eijirou is just as bad.

“Alpha.” He acknowledges.

This is a dangerous game they’re playing into. Delving into their needs like this. Katsuki doesn’t have to prove shit to anyone, least of all Eijirou who knows him - him, not just his alpha - and continues to want him.

But Eijirou’s eyes on him are like a searing prod to hide. Sunshine touching the the endless plains, keeping the world warm.

This is a dangerous game for them to start. But everyone here knows them - knows him.

Like anyone who knows him, they know he lives for the burn.

Tilting his head down, Katsuki steels himself. “Watch.”

It's different for every alpha, but because it's him, he starts with his chest.

Katsuki sucks in a deep breath. Rolling both shoulders once, before doing it again and holding them in place. His whole posture changes as he pushes back his arms. Straightens his shoulders.

He raises his neck, keeping it long, tight. Exposed. Fearlessly displaying both glands.

Abdomen tightened. Corded muscles flexing easily up his arms and legs.

He feels big. Strong. Powerful. Standing like this, on full display. Everything exposed.

Eijirou's eyes are roaming all over, shimmering like the embers from a fire.

It's the high kind of feeling an alpha could get off to.

Then, someone has to make a loud, obnoxious gasp behind him.

"Holy shit! I think Kacchan's trying to present to Ei!"

His teeth fall together, clasping into a grind. Fangs on the cusps of popping out.

Katsuki isn’t trying for shit. There’s no competition; Eijirou’s eyes are completely on him-

Except they’re not. Too busy fluttering around with all that extra noise.

It’s an overwhelming sensation, suddenly. Like water running over his ears. Sand thrown in his eyes. Lead holding down his tongue.

Eijirou isn’t looking. Katsuki’s in full stance and he isn’t watching.

He’s presenting to his omega. His omega shouldn’t be looking elsewhere. Only on him!

The smell of foreign alpha lingers on his skin. The smell of courting competition.

If it was a game before, it’s all out war now.

Katsuki’s the alpha for him!

Without missing a beat, not breaking stance at all, Katsuki lets out a low, feral snapping bark.

It takes mere seconds for those roaming, crimson eyes to snap back on him. But it’s only those seconds he needs for the omega to see-

Katsuki gripping his cock through his sweats - practically in a vice - while moving his hand up the length of it, all for Eijirou to see.

“Omega.” He growls, something deeper, darker twinging along his tongue.

He grips himself harder, barely making a hiss.

“Knot you.” He swears - with his words and tensely focused eyes. “Big knot. For you. All of it...in you.”

Eijirou’s eyes don’t move as soon as they fall upon the outline of his fat, alpha cock.

He makes a sound out of his throat - pitchy and loud - close to one of the ones he makes through their shared walls occasionally. Driving Katsuki out of his fucking mind while they separate for his heats.

Sometimes, when they pretend Katsuki’s going to give him the bite, the alpha can get him to sound like that while they fuck.

But right now, full-presenting, showing an omega his very fertile package.

Katsuki feels like someone’s released hornets into his fucking chest.

He doesn’t even realize he’s oozing pheromones until someone speaks up.

“Dammit Denki! Why did’ya have to open your big mouth! Now everyone’s going to pop a presenting knot!”

Presenting knots. The true way to offset a challenging suitor alpha.

If an omega had more than one alpha to choose from, of course they were going to pick the one with biggest, breeding knot.

His sweats already felt heavy with his dick swelling in them.

His knot was going to drop his goddamn pants.

Damn. Fuck. Katsuki reaches down to adjust. He’s not wearing any shorts underneath and already Eijirou’s getting an eyeful of curly blonde hairs-

There’s nothing graceful about the way his hand gets slapped away from gripping the grey stretch band to his sweats.

It leaves him in shock for a second.

Eijirou’s growl is deeper than most omegas.

It’s a sure fire way to get Katsuki’s cock to twitch.

He’s closer now, less leaning back on the couch and more sitting up straight. Filling the space in between them. Posture straight, chin lowered so his growl perforates louder from his throat.

Katsuki stares at him all with awe, maybe a little trepidation.

T O P https://twitter.com/superliddy/status/1383154280169881604

Eijirou’s eyes aren’t the same ones that were watching him seconds ago. His pupils are still blown, but now in between slitted lids. Staring only where he’d just slapped the alpha’s hand away from his knot.

He smells honey warmed, but not the same way it hits when he’s happy.

There’s a hard nudge against his hip.

“Alpha,” the omega says in a low, demanding tone, “keep presenting.”

There’s a flutter of dark eyelashes. “I can’t tell how big your knot is-“

Katsuki feels his entire body turn stone.

“-my omega doesn’t know if it’s you we should pick yet.”