Chapter Text
Izuku wakes to the sound of his phone going off, vibrating against his bedside table. With a groan, he slaps his hand down on the wood, searching blindly until he finds his phone. He swipes at the screen and, squinting against the harsh light in his otherwise dark room, holds it up against his ear.
“Hello?” he croaks, voice still rough with sleep.
“Midoriya Izuku?” A woman on the other end asks.
“Yeah, that’s me, who’s this?” he asks around a yawn, rolling over in his nest of blankets to check the time on his clock. It’s nearly 3 AM.
“My name is Yaoyorozu, um, pro hero Creati. I’m with Best Jeanist’s agency. One of our heroes has had a run in with a villain and their quirk jump started his rut. Unfortunately, the sedation drugs and Quirks we’ve tried have had no effect. I understand that you’re a volunteer omega that helps out in this sort of situation?”
“Oh!” Instantly, Izuku’s wide awake. He sits up in bed and immediately starts fangirling. “Oh my god, yes, hi! Wow, I can’t believe I’m talking to pro hero, Creati!” He laughs nervously and the pro hero delicately clears her throat.
“Does that mean you’re willing to service the alpha in question?”
“Oh, oh yes, of course!” Izuku replies quickly.
Born without a Quirk, Izuku was never able to pursue his dream of becoming a pro hero, so he had to look for other ways to feel useful. Izuku may not have a Quirk, but he did present as an omega, a rare secondary gender that comes with heats and the ability to carry a litter. It also means that he has the ability to calm an alpha in rut by mating with them.
So, a couple of years ago, Izuku signed up for a certain volunteer program where, in the event that an alpha pro hero goes into a rut, he might be called upon to them through it. It was so long ago, though, that he sort of forgot all about it. “Do you, um, need me right now?”
“Please,” she says, voice strained. “He’s tearing up one of our rut rooms as we speak. I think it’ll hold but,” the sound of a muffled explosion interrupts her, “we really don’t want to risk it,” she finishes in a half-shout over the commotion.
“I understand,” Izuku replies, already scrambling out of his sheets. “I’ll be there as soon as possible.”
“Thank you,” she sighs in obvious relief. “Please hurry,” she adds and Izuku hears the sound of another explosion going off in the background before the line clicks dead.
Izuku rolls out of bed and races to get dressed, heart pounding. He stuffs his feet into his shoes and tugs a hoodie over his head, shoving his keys and wallet into his pockets as he rushes out the door.
While on his way to the agency, he wonders which pro hero he’s going to service and what kind of Quirk could activate a rut in the first place. He jots down notes on his phone, muttering to himself about possible theories on how such a Quirk might be triggered (most likely scent or touch) and how long the effects last.
Twenty minutes later, he’s standing outside the rut room at Best Jeanist’s agency. Izuku swallows thickly as he watches his estranged childhood friend, Bakugou Katsuki, better known as pro hero Ground Zero, rage inside the rut room. His face is red as he screams a nearly incoherent string of profanity, explosions popping along his palms.
“How long has he been like this?” Izuku asks quietly.
“Well over an hour,” Yaoyorozu, pro hero Creati, sighs. “And he’s shown no signs of slowing down.” Nervously, she glances at the armored door as the alpha inside lets off another explosion that rocks the floor they’re standing on. “I understand if you want to back out. No one will blame you.”
Izuku bites his lip, hesitating. Out of all the pro heroes he expected, his childhood friend Kacchan was not one of them. Izuku almost wants to laugh at the irony of the situation. Because for as long as he can remember, he’s been in love with the alpha.
The two of them grew up together. Kacchan was born with a sharp mind and natural athleticism. He was also blessed with an amazing Quirk, perfectly suited to hero work. Izuku, always so enraptured by heroes, of course admired the young alpha’s strength and passion, his confidence and brilliance. Kacchan was amazing at everything he put his mind to and he became Izuku’s symbol of victory. So it was no wonder that the omega fell in love with him.
Loving Kacchan came so naturally to him that Izuku’s not really sure there was ever a time when he didn’t love the alpha. At this point, Izuku doesn’t think he could stop loving him even if he tried. However, the more Izuku admired him, the more it made Kacchan angry.
He kept pushing Izuku away until, by the time they graduated middle school, the only time Kacchan acknowledged his existence was to make fun of him. After that, they went their separate ways, attended different high schools: Kacchan to the prestigious UA to become a hero, Izuku to a private all-omega school on a scholarship, and they lost touch. By then, Izuku had lost all hope that the alpha would ever reciprocate his feelings.
Life went on, though. Izuku made friends, even dated around, but he never really got over his first love. He still feels an ache in his chest whenever he sees Kacchan on TV, amazing and handsome as always after a daring rescue or a spectacular fight. Ground Zero is a hero on the rise and he’s everywhere: billboards and ads plastered on the train with the alpha’s face, sharp red eyes glinting above his devilish smirk as he runs a hand through his wild blond spikes.
Looking at him now, even in the middle of a rut rage, Kacchan is as handsome as ever, and Izuku feels that sweet ache in his heart at the sight of his childhood friend. Kacchan’s still in his hero uniform, black tank top ripped and singed in places from his own explosions. Izuku admires the alpha’s impressive back, the thick muscles in his shoulders and arms flexing as he screams wordlessly and sets off another explosion with his palms.
Maybe after everything the alpha put him through, Izuku should feel some kind of vindictive pleasure watching him suffer now, but no matter what Kacchan said or did in the past, Izuku can’t find it in his heart to hate him. All he feels when he looks at him now is that long familiar ache, that desperate longing to be acknowledge by the most important and influential person in his life. So even if Kacchan hates him, even if he doesn’t want his help, even if it means crossing some kind of moral or ethical line, Izuku won’t leave him to suffer through a rut alone.
“I’ll do it,” he says.
“Are you sure?” Yaoyorozu asks. “There are risks, he could easily hurt you. Of course we will monitor the situation and try to extract you if it becomes too dangerous, but we can’t guarantee your safety.”
Izuku nods. “I understand the risks, but I’m not afraid. He won’t hurt me.”
“Very well,” she says and hands him the consent forms. Izuku’s hand is steady as he signs them. He barely acknowledges the warnings and risks, signs the nondisclosure agreement without question, and hands back the clipboard.
Yaoyoruzu gives him a slight bow, relief written clear across her face. “Thank you for your service, Midoriya. Please take care of him.” Another explosion rocks the ground under them and, as she straightens, she flashes him a worried look. “Please take care of yourself as well.”
Izuku nods and flashes her his best reassuring smile before reaching for the door. “Please forgive me, Kacchan,” he whispers as he steps into the rut room. He sucks in a deep breath to steady himself and nearly moans as he inhales the alpha’s heady scent. God, it’s just like he remembers. Like gunpowder and caramel, so sweet and powerful it makes his head spin. It might as well be an aphrodisiac for the way it sets his blood on fire, lust scorching through his veins to pool hot and heavy in his belly.
The second Kacchan senses his presence, he halts mid-tantrum, nose in the air as he picks up Izuku’s scent. He whirls around, sharp, angular features twisted in a vicious snarl, and his palms explode as he launches himself across the room. He slams into Izuku like a ton of bricks, a solid wall of muscle that tackles him to the ground and knocks the breath from his lungs. The back of his head bounces off the floor and Izuku cries out in pain. He lies there, dazed and disoriented, as the snarling alpha tears at his clothes, shredding them to ribbons until he’s spread out and naked under him. In one smooth motion, Kacchan flips him over. Vaguely, Izuku hears the sound of ripping fabric but before he can register what’s happening, Kacchan hauls him back by the hips and slams into him.
“Ah, Kacchan!” Izuku screams as he’s abruptly filled to the brim with the alpha’s massive, throbbing cock. It’s too much, too fast, and Izuku has to fight through the initial panic, nails scraping against the floor as he tries to get away. Behind him, Kacchan snarls viciously. It’s the only warning Izuku gets before the alpha sinks his fangs into the scruff of Izuku’s neck to stop him from struggling. Like flipping a switch, Izuku goes limp, pleasure fogging over his mind as Kacchan starts rutting into him.
Ferocious snarls spill from between his fangs and warm blood dribbles between his lips and over the omega’s skin as he fucks into him ruthlessly. Hips slapping against Izuku's ass in a frantic rhythm, Kacchan tries to force his knot inside Izuku’s tight, clenching walls. Izuku cries out, his body jerks under his alpha’s with every sharp thrust, and tears spill down his cheeks as he lies there and takes it. It feels so good, so right. He was built for this, built to take his alpha’s knot, drooling and begging for it as he’s fucked and filled over and over until he’s big and round with his alpha’s cum.
“Kacchan, ah, Kacchan, yes! Yes! Breed me, please, Alpha!” Izuku begs. Behind him, his alpha snarls, palms popping with tiny explosions along Izuku's hips and he wails, his own cock throbbing and aching, leaking freely as it bobs between his legs. With one final, brutal thrust, Kacchan forces his knot through the tight ring of muscle. Izuku tosses his head back and howls, his release splattering across the floor as Kacchan’s knot pops into place and locks them together. Kacchan pries his fangs out of the scruff of Izuku’s neck to nuzzle his tear-stained cheek affectionately, chest rumbling with a deep purr as his lips leave a bloody trail across Izuku’s cheekbone. Izuku’s so blissed out from being knotted and bred that all he can do is moan weakly.
Kacchan drags his hot, wet tongue over the imprint of his fangs, warm breath fanning out over Izuku’s skin, and he shivers in anticipation as his alpha’s lips ghost down the back of his neck. Kacchan follows the curve of his shoulder, then, without warning, he bites into the meat of Izuku’s shoulder. Sharp pain shoots up Izuku’s spine and he wails, thrashing weakly under his alpha. Kacchan growls and bites down harder, his hold on Izuku’s hips turned bruising as he holds him down and starts to grind against him. Izuku moans when he feels Kacchan’s thick cock start throbbing in his ass, emptying the first of many waves of his hot seed deep inside him.
"Kacchan, oh, Kacchan, yes!" With a breathy cry, Izuku spreads his legs wider and eagerly pushes himself back on Kacchan’s knot, desperately trying to take him deeper. Face pressed into the floor, drool pooling under his cheek, Izuku grinds back against his alpha’s knot, squeezing and milking it for every last drop of his warm cum. Kacchan keeps bucking against his ass, knot tugging gently at his rim as he keeps pumping him full of his seed. Izuku sags against the floor. He feels like he’s floating, drifting on a warm cloud, head blissfully empty for once as Kacchan breeds him.
As soon as his knot goes down, he pulls out, and Izuku whimpers pitifully, heart aching as his alpha separates from him.
“No,” he whines, seed spilling down his trembling thighs. “Kacchan….” It’s getting away, he wants to say.
Sensing his distress, Kacchan rolls him over, crooning in reassurance as he pries Izuku’s legs apart. His alpha’s soft palms slide over the sensitive skin of his inner thighs as he hooks Izuku’s legs over his hips. He pushes the fat head of his cock against the puffy, twitching rosebud between Izuku’s legs. Kacchan rocks against him, the tip of his cock catching on Izuku’s wet, stretched rim, and Izuku moans, the muscles in his legs straining as he tries to spread them even wider. He’s so unbearably empty, his hot core aching and throbbing with need, he’s desperate to be fucked and filled, stuffed with his alpha’s massive knot and rich cum.
“Alpha,” he whines, rocking his hips, trying to get his alpha to sink into him. Kacchan bares his fangs as he starts to force his searing length through the tight ring of muscle inside him and Izuku whines, flashing his throat in submission. Above him, his alpha snarls in approval, then his hips snap forward as he thrusts all the way into the hilt. Izuku wails, spine arching up off the floor. The pain adds a sharp, delicious edge to his pleasure. He feels like he’s being split open, like his insides are being molded to the shape of his alpha’s massive cock. The thought makes his toes curl and Izuku’s trembling thighs clamp down around Kacchan’s hips, heels digging into the small of his back to pull him deeper.
“Kacchan!” Izuku cries out in ecstasy, nails biting into Kacchan’s arms. Grunting with the effort, he rolls his hips and grinds into Izuku over and over, rubbing against the tight bundle of nerves deep inside him with every roll of his hips. It sends almost continuous shocks of pleasure up Izuku’s spine and his cock twitches against his belly, mouth open around a string of nearly incoherent moans and garbled renditions of Kacchan’s name. Hands slipping on sweaty skin, Izuku grasps weakly at his alpha’s broad shoulders and thick arms, desperately trying to ground himself, but he’s quickly swept under by a riptide of pleasure. He chokes around a sob, staring up at Kacchan in awe.
He’s always been beautiful, but Izuku’s never seen him like this, so savage and fierce that it’s almost terrifying. He’s gone completely feral, pupils slit and irises bright like hot coals as he glares down at him. Izuku feels like he’s burning up under that intense stare, growing hotter and hotter as the pleasure builds. His cries ratchet higher the closer Kacchan drives him to the edge. Back arching off the ground, Izuku’s thighs strain in his alpha’s bruising grip as his hips twitch uselessly against the air, pretty pink cock leaking freely against his belly.
Everything feels so good. Kacchan's fingers dig into the soft flesh of his thighs as he pulls them even farther apart to fuck him deeper, harder, and all Izuku can do is lie there and take it until he’s a sobbing, fucked out mess.
“Oh my god!” he keeps wailing, tears running from the corners of his eyes and into his hair. “Oh my god, Kacchan! ”
The alpha growls viciously and hauls his hips up higher, starts fucking into him faster. The sounds he’s making, these constant, feral snarls tearing out of his throat drowns out even the wet, lewd sound of their hips frantically slapping together as their pleasure reaches a fever pitch. Whole body strung taut, Izuku nearly bends himself in half, back bowing as he comes across his belly in white hot streaks. Stars pop behind his eyes as Kacchan holds him open and ruthlessly fucks him through it. Loud snarls fall from his lips as he forces his cock in and out of Izuku’s clenching ass over and over, until, with a roar, he finally shoves his knot through the tight ring of muscle.
Izuku holds still, shaking under his alpha as he tests the strength of their tie. Gently, Kacchan rocks his hips and Izuku whimpers when he feels his alpha’s knot tugging gently at his rim. When it holds and they stay locked together, Izuku moans. Chest rumbling with approval, Kacchan drapes his heavy, sweaty body over Izuku’s, cock twitching where it’s buried deep in his ass as he starts to come.
The omega moans. He can feel it, the sensation of Kacchan coming inside him, filling his belly with wave after wave of his hot seed. Legs trembling, nails scrabbling against the floor, Izuku desperately tries to hold onto something as his second orgasm crashes over him. He shakes apart in his alpha’s hands, cries out and paints his belly with sticky white stripes as he comes again, slick pouring out around his alpha’s knot, ass rippling and clenching around it like he’s trying to milk him dry. With a groan, Kacchan keeps bucking into him, cock pulsing as he fills him with another load.
When he comes to, Kacchan’s crooning to him again, eyes locked on the omega’s distended belly, reverently smoothing his hands over it. "Kacchan," Izuku moans weakly. He feels his alpha’s cock throbbing in him again as he pumps him full of white hot seed. Head spinning, strung out on Kacchan’s powerful alpha pheromones, Izuku lets his head fall back against the floor, body gone completely limp and pliant.
“Alpha,” he slurs brokenly, a string of drool sliding out of the corner of his open mouth as Kacchan draws his legs over his shoulders, eyes half lidded as he practically bends Izuku in half before sinking into him again.
Everything after that bleeds into a colorful haze of mind numbing pleasure. He becomes little more than Kacchan’s living, breathing fuck doll as his alpha pushes and pulls at him, positioning him however he likes as he fucks him relentlessly. Izuku passes out in the middle of being mounted and knotted from behind only to jerk awake to Kacchan fucking him against a wall sometime later. He’s not sure how long it’s been. Hours, days, weeks, Izuku’s lost all sense of time, mind completely shot from the overwhelming pleasure of being knotted and bred so many times.
By the time it’s finally over, Izuku can hardly move. He’s taken so many loads that he looks pregnant, belly full of Kacchan’s hot cum. Every time he moves, he swears he can feel it sloshing around inside him. He’s never felt so wonderfully full. It leaks out around his alpha’s knot where they’re tied together and slides down his bruised thighs as he stretches out under his alpha, chest rumbling with a content purr.
Kacchan growls back affectionately, nosing at the the aching scent glands under Izuku’s jaw. Izuku nuzzles back and answers him with a soft whine, throat raw from screaming out his pleasure for the last several hours. Kacchan drags his tongue across Izuku’s scent glands and he tilts his neck to the side, offering himself up. Kacchan’s chest vibrates with a rumbling purr as he sucks on the omega’s sensitive glands. Izuku shivers and cries out, squirming on his alpha’s knot, shamelessly begging to be claimed. Teasingly, Kacchan scrapes his fangs against Izuku’s gland one more time before biting down, fangs sinking into him as easily as biting into an overripe cherry. His blood bursts sweet and warm over Kacchan’s tongue and Izuku wails, nails scratching down his alpha’s back as he’s claimed. His whole body seizes, every nerve ending lit up as the bond snaps into place. It’s the most intense pleasure he’s ever known, so intense that he blacks out.
The next time Izuku cracks his bleary eyes open, he feels like he’s been hit by a truck. His hips and ass are particularly sore, but he also feels safe, warm, and sated. With a yawn, he stretches languidly and tries to roll over, but the muscular arm draped over his waist tightens. Izuku’s eyes snap open as he’s tugged back against a solid chest and he freezes when he feels someone nosing against his throat, warm breath fanning out across his fresh bond mark.
“Deku,” Kacchan growls, lips brushing against his skin. “What the fuck is going on?”