The first thing Izuku feels is the dried, tacky evidence of Kacchan’s claim plastered across his inner thighs and lower belly. The second thing he feels is the heavy, muscular arm slung possessively over his waist, pinning him to the mattress. The third thing is the immediate, slick heat between his own legs, a throbbing ache that has nothing to do with soreness and everything to do with want. He’s still full. A deep, liquid weight sits low in his pelvis, a reminder that last night wasn’t a dream. He shifts, and he feels it—the subtle slosh, the pressure against his bladder, the undeniable proof that Kacchan emptied himself inside and sealed it there.
Kacchan’s nose is buried in the crook of his neck, breathing deep. Izuku can feel the puffs of warm air, the slight twitch of the dog ears against his own cheek. He doesn’t move. He just lies there, cataloging the sensations. The smell of them—sex, rain, musk, salt. The way his small buds are tight and sensitive against the sheets. The way his pussy is already wet again, his body betraying him before his mind even catches up. He’s ruined. He’s perfect.
“You’re awake.” The voice is a sleep-roughened growl against his skin. It isn’t a question.
Izuku’s breath hitches. “Yeah.”
“Good.” Kacchan’s arm tightens, pulling him backwards until Izuku’s back is flush against the solid wall of his chest. The thick, hardening length of him presses against the cleft of Izuku’s ass. It’s already emerging from its sheath, hot and insistent. “Need you.”
A shiver runs through Izuku, head to toe. It’s not a request. It’s a statement of fact, as simple as saying the sky is gray. He needs. So he will have. Izuku’s hand finds Kacchan’s where it rests on his stomach, lacing their fingers together. He guides that broad, calloused palm lower, over the soft curve of his belly, down through the coarse thatch of hair, until Kacchan’s fingertips are pressing against his own slick folds.
“It didn’t go away,” Izuku whispers, his voice trembling. “The feeling. The need. It’s worse.”
Kacchan nips at his shoulder, a sharp, claiming bite. “Mine.” His fingers slide through the wetness, circling his entrance, already stretched and soft from the night before. “Always worse. Always more.”
He doesn’t tease. He pushes two thick fingers inside, and Izuku arches with a broken cry. He’s so open, so ready, his body accepting the intrusion with a grateful clench. Kacchan crooks his fingers, and Izuku sees stars, his toes curling into the sheets. “K-Kacchan—”
“Tell me.”
“I need it. Please. I need your… your cock.” The word is filthy and perfect in his mouth. “I need you to fill me up again.”
Kacchan withdraws his fingers, bringing them to his own mouth to lick them clean. Izuku watches, mesmerized, as those red eyes darken. “Taste like me. And you.” He rolls Izuku onto his stomach with effortless strength. The movement makes the liquid inside Izuku shift, a warm, intimate slosh that has him moaning into the pillow. “On your knees. Now.”
Izuku scrambles to obey, his body thrumming with anticipation. He gets his knees under him, ass in the air, face pressed into the pillow that smells like them. He feels exposed, wanton, presented. Behind him, he hears the wet sound of Kacchan stroking himself, a low growl rumbling in the man’s chest.
“Look,” Kacchan commands, his voice guttural.
Izuku cranes his neck, looking back over his shoulder. Kacchan is kneeling behind him, his muscular thighs spread, one hand fisting the base of his fully erect cock. It’s a brutal, beautiful sight—the thick red shaft, the prominent veins, the swollen bulb of the knot already forming at the base. Pre-cum beads at the slit, dripping onto the sheets. Izuku’s mouth waters.
“You see what you do?” Kacchan snarls. “This is yours. Only yours.”
The tapered head presses against Izuku’s entrance. He’s so wet it slides through his slick folds, bumping against his clit, making him jolt. “Please,” Izuku begs, pushing his hips back. “Please, I can’t wait, just—”
Kacchan drives forward.
The stretch is exquisite, a burning, perfect fullness that steals the air from Izuku’s lungs. He’s still loose from the night before, but Kacchan is so thick, so impossibly huge, that it feels like the first time all over again. He sheathes himself in one long, relentless thrust, until his hips are flush against Izuku’s ass, until Izuku can feel the press of that developing knot against his stretched rim.
“Fuck,” Izuku sobs, his fingers clawing at the sheets. He’s so full, so completely claimed. The weight in his belly is compounded, pressure building in a delicious, overwhelming way.
Kacchan doesn’t let him adjust. He sets a punishing pace from the start, pulling out almost all the way before slamming back in. The sound is obscene—wet skin slapping against skin, the squelch of Izuku’s dripping cunt taking him, their ragged breaths. Each thrust jostles the cum already inside him, making him feel like a overfull vessel, like he’s being used and remade with every drive of Kacchan’s hips.
“Mine,” Kacchan grunts, his hands gripping Izuku’s hips hard enough to bruise. “My mate. My breeder.”
The word—breeder—sends a violent thrill through Izuku. His orgasm crashes into him without warning, a tidal wave of pleasure that wrenches a scream from his throat. His cunt convulses around the massive cock splitting him open, milking it, and he feels the hot gush of his own release adding to the mess between his legs. Kacchan doesn’t stop. He fucks him through it, his rhythm growing more erratic, more desperate.
“Gonna knot you,” Kacchan pants, his thrusts becoming shorter, harder. “Gonna lock in. Fill you up. Again.”
The knot swells rapidly, a relentless pressure that burns as it stretches Izuku wider, wider than he thought possible. It catches on his rim, and Kacchan gives one final, brutal shove, burying it deep inside. Izuku feels the pop, the sudden, total fullness that borders on pain. He’s stuffed, impaled, completely immobilized.
Kacchan roars, his body going rigid. Izuku feels the first hot pulse deep in his core, a flood of fresh cum joining the old. Another pulse. Another. It seems to go on forever, pumping into him, adding to the bloated, heavy feeling in his belly. Kacchan collapses over him, his weight driving Izuku further into the mattress, his teeth sinking into the juncture of Izuku’s neck and shoulder as he rides out his climax.
They stay like that, locked together, for a long time. Kacchan’s chest heaves against Izuku’s back. Izuku can feel the frantic beat of his heart, or maybe it’s his own. The knot keeps him achingly full, and every few moments, he feels another weak spurt, another claim.
“So much,” Izuku slurs, dazed. His hand drifts to his lower stomach, pressing. He can feel the slight, firm roundness. “You’re putting so much in me.”
“Not enough.” Kacchan’s voice is muffled against his skin. “Never enough. Gonna drown you in it. Gonna make sure it takes.”
The possessiveness in his tone should be frightening. It just makes Izuku clench around the knot, drawing a ragged groan from the man above him. He wants that. He wants to be drowned. He wants to be so full of Kacchan that he can’t think of anything else.
When the knot finally deflates enough for Kacchan to slip out, a rush of fluid follows—a mixture of old and new, hot and slick, pouring out of Izuku and onto the sheets. He whimpers at the loss, at the emptiness, even though he’s still dripping.
Kacchan rolls him onto his back. His crimson eyes scan Izuku’s face, then drop to his chest, his belly, his ruined pussy. He looks ravenous. “Again.”
Izuku nods, breathless. “Yeah.”
They don’t leave the bed. The sun climbs higher, filtering through the rain-streaked window. They fuck in the gray light. Kacchan lays Izuku on his back, hikes his thick thighs over broad shoulders, and eats him out until he’s sobbing, until he squirts into that demanding mouth. Then he flips him over, mounts him from behind, and knots him a second time, his cum joining the pool already inside.
They break only to drink water from the glass on the nightstand, Kacchan holding it to Izuku’s lips, watching him swallow. Izuku’s body is a map of bites and bruises and drying come. He’s never been so thoroughly used. He’s never felt so alive.
“Why?” Izuku asks later, his head pillowed on Kacchan’s chest. They’re on their sides, facing each other. Kacchan’s fingers are tracing idle patterns on the small, soft curve of Izuku’s belly. “Why… all of this? The…” He flushes, gesturing weakly between his legs.
Kacchan’s gaze is unwavering. “Mate.” As if that explains everything. Maybe it does. “My scent in you. My claim. It… marks. It breeds.” He says the words with a simple, feral certainty. “You take it. You want it.”
“I do,” Izuku admits, the truth of it a quiet hum in his veins. “I really, really do.”
“Good.” Kacchan leans in, catching Izuku’s lips in a kiss that’s surprisingly soft. It tastes like salt and sweat and them. When he pulls back, his eyes are intense. “More.”
He coaxes Izuku onto his lap, his back to Kacchan’s chest. Izuku sinks down onto his cock slowly, achingly, taking every inch until he’s seated fully, Kacchan’s thickness stretching him wide. They rock together like that, a slow, grinding rhythm that’s less about frenzy and more about possession. Kacchan’s hands roam over Izuku’s body—palming his small buds, pinching his puffy nipples until Izuku cries out, then soothes them with his thumbs.
“You feel it?” Kacchan murmurs into his ear, his hips rolling up to meet Izuku’s downward slide. “Inside? All of me?”
“Yes,” Izuku gasps. He’s so sensitive, every movement a lightning strike of pleasure. “I feel you everywhere.”
“Good.” Kacchan’s hand slides down Izuku’s front, through the trail of coarse hair, his fingers finding Izuku’s clit. He rubs tight, fast circles, and Izuku comes apart, screaming, his cunt clamping down on the cock inside him. That’s all it takes. Kacchan follows him, his knot swelling rapidly, locking them together in this intimate, seated embrace. The fresh flood of heat makes Izuku’s overspent body shudder.
The afternoon bleeds into evening. They lose count. Izuku rides him on all fours. Kacchan fucks him against the wall beside the bed, one of Izuku’s legs hooked over his arm. Each time ends the same: with the swell of the knot, the deep, claiming release, and the temporary, blissful lock that binds them. Izuku’s belly grows progressively more rounded, a soft, distinct pouch of fluid that he can’t stop touching. He’s sloshing with it. He’s made of it.
As dusk settles, Izuku is lying on his side, utterly spent. His body feels liquid, boneless. He’s sore in the best way. Kacchan spoons behind him, one arm draped over his waist, his palm splayed possessively over the slight swell of Izuku’s stomach. They’re both sticky, filthy, reeking of sex and claim.
Kacchan nuzzles the back of his neck. “Hungry?”
Izuku shifts against the sheets, the movement sending a fresh trickle of release down his inner thigh. His body is a map of exhaustion, every muscle liquid and sore, but the ember in his gut hasn’t died. It smolders, fed by the weight in his belly and the possessive arm around his waist. He nods, a slow, drowsy movement. “Yeah.” His voice is a ruined rasp. He turns his head slightly, his cheek brushing Kacchan’s bicep. “But not for food.”
Kacchan stills behind him. The nuzzling at his neck stops. His palm presses more firmly against the soft swell of Izuku’s stomach.
“I’m hungry for you,” Izuku whispers into the dim room. The confession feels as raw as the stretch marks he imagines forming on his skin. “For what you put in me.” He swallows, his throat dry. “Feed me, Kacchan. Your cum. Fuck my mouth with it. Fill my stomach like you’ve filled my… like you’ve filled my womb.”
A low, vibrating growl answers him. Kacchan’s arm tightens. “Mouth.”
“Yes.” Izuku’s pulse kicks, a frantic drum against his ribs. The idea is filthy, degrading in a way that sends a bolt of pure heat straight to his spent cunt. He wants to be a vessel in every way. He wants to drink the proof of his own claiming. “Please.”
Kacchan moves. He rolls Izuku onto his back with a single, powerful motion. The shift makes the fluid inside Izuku slosh audibly, a wet, intimate sound. Kacchan looms over him, his crimson eyes reflecting the last dusky light from the window. He looks feral, pleased, his sharp teeth bared in something that isn’t quite a smile. He’s already hard, his thick canine cock standing rigid against his lower abdomen, the head gleaming with pre-cum.
“Open,” Kacchan commands, his voice gravel.
Izuku obeys without hesitation. He parts his lips, his tongue resting against his bottom teeth. His heart is hammering, a frantic rhythm that has nothing to do with fear and everything to do with a desperate, aching need to be used.
Kacchan doesn’t tease. He fists his cock, gives it two rough strokes, and guides the broad, tapered head to Izuku’s mouth. The taste hits Izuku first—salty, musky, uniquely Kacchan. It’s the taste he swallowed in the bath, the taste he’s been leaking all day. He moans around it, the sound vibrating against the sensitive flesh.
“Take it,” Kacchan grunts, and he pushes forward.
Izuku gags immediately. He’s unprepared for the sheer girth, the way it stretches his lips and presses against the back of his throat. Tears spring to his eyes. He chokes, his hands coming up to clutch at Kacchan’s thighs.
“Breathe through your nose,” Kacchan says, not pulling back. His thumb strokes Izuku’s cheek. “Relax your throat. Take your mate.”
Izuku forces himself to inhale, a shaky, wet sound. He wills his muscles to unclench. He lets his jaw go slack, lets his throat open. Kacchan pushes deeper, and this time, the head slips past the tight ring of muscle. Izuku feels it, a profound, invasive fullness in his mouth and throat. He gags again, but softer this time, his body learning.
“Good,” Kacchan praises, his voice a dark rumble. He pulls back slowly, then pushes in again, a little deeper. “So good for me. Taking me everywhere.”
Izuku’s eyes drift shut. The sensation is overwhelming. The stretch of his lips, the pressure on his tongue, the hard heat at the back of his throat. The taste is everywhere, coating his mouth, sinking into his senses. He feels owned in a new, devastating way. His pussy, sore and dripping, clenches around nothing.
Kacchan sets a slow, deep rhythm. He isn’t frantic. This isn’t about his own release yet. This is about feeding. About claiming. Each thrust is measured, pushing Izuku’s limits, making him take a little more each time. Saliva drips from the corners of Izuku’s stretched lips, down his chin, onto his neck. The wet, sucking sounds are obscenely loud in the quiet room.
Izuku’s mind goes blank, blissfully empty. There is only the cock in his mouth, the hand cradling his head, the growled praise. He surrenders to it completely, letting Kacchan use his throat, his mouth becoming just another part of him being filled.
“Gonna cum,” Kacchan announces, his hips starting to stutter. His rhythm loses its precision, becoming faster, harder. “Gonna feed my mate. Swallow it all.”
Izuku opens his eyes, looking up. Kacchan’s face is a mask of fierce concentration, his brows drawn, his lips pulled back from his teeth. His crimson eyes are locked on Izuku’s, holding him there. The eye contact is more intimate than the penetration. Izuku can’t look away.
Kacchan drives deep one last time, burying his cock to the root. Izuku’s nose is pressed against the coarse hair at the base. He gags, tears streaming freely now, but he doesn’t fight it. He takes it.
Kacchan roars, a raw, animal sound. The first spurt hits the back of Izuku’s throat, hot and thick. Izuku swallows reflexively, the bitter-salty flavor flooding his senses. Another pulse. Another. Kacchan holds himself there, grinding shallowly as he empties himself down Izuku’s throat. Izuku swallows and swallows, his throat working around the pulsing shaft, taking every drop he’s given.
It seems to go on forever. A seemingly endless flood. Izuku feels it hit his stomach, a warm, heavy weight. He’s being filled from both ends, claimed inside and out. The thought makes him dizzy, makes his oversensitive body shudder.
Kacchan doesn't pull out. The pulsing softens, but he stays buried in Izuku’s throat, his grip on Izuku’s hair tightening. A different pressure builds at the base of Izuku’s tongue, a deep, internal shift. Izuku’s eyes, wet and blurry, fly open wide. He knows this feeling. It’s not another orgasm.
A hot, bitter stream hits the back of his throat. It’s sharper than the cum, a salty, acidic flood that makes him gag instinctively. Kacchan holds him fast, a low, approving growl vibrating through his belly and into Izuku’s face. “Swallow,” he rasps, the command muffled by flesh.
Izuku obeys. He swallows convulsively, the warm liquid burning a path down to join the heavy weight in his stomach. It’s too much. It’s everything. A broken, wet moan works its way up around the cock in his mouth, a sound of shocked, absolute surrender. He drinks him down, accepting this too, this deepest mark.
Finally, the stream trickles to a stop. Kacchan pulls out slowly, his slick cock dragging over Izuku’s tongue. Izuku collapses back, coughing, spit and tears and the last traces of bitter salt dripping from his chin. He’s panting, his mind white noise.
Kacchan moves with purpose. He hauls Izuku up by the arms and flips him. Before Izuku can process, he is straddling Kacchan's chest, facing the headboard. He hooks his hands under Izuku’s thighs and pulls, dragging Izuku’s hips up until his dripping, swollen cunt is positioned directly over Kacchan’s face.
“Now you,” Kacchan says, his voice rough with intent. He nuzzles into Izuku’s folds, his tongue swiping through the slick and cum from earlier. He licks a slow, deliberate stripe. “Mark me inside. Piss in my mouth.”
The command cuts through Izuku’s daze. His bladder is painfully full, a tight, aching balloon low in his belly. The idea is terrifying. It’s obscene. A fresh, sharp thrill arrows through his exhaustion. “I… Kacchan…”
“Do it.” Kacchan’s mouth closes over his clit, sucking gently. The pressure is an electric shock straight to his bladder. “Give it to me. Your claim.”
Izuku whimpers. He’s never done this. He’s never even thought it. He squeezes his eyes shut, focusing past the overstimulation, past the shame, finding the deep, urgent pressure within. He lets go.
The release is a hot, desperate gush. It splashes over Kacchan’s waiting mouth, his tongue, his chin. Izuku hears the wet sound, feels the warmth spill over his own skin. He moans, high and shaky, the relief so profound it borders on pain.
Kacchan drinks. He swallows audibly, greedily, his throat working against Izuku’s inner thigh. A ragged, pleased groan vibrates into Izuku’s pussy. He doesn’t spill a drop, taking every ounce Izuku gives him, lapping at the stream until it slows to a trickle, then licking Izuku clean with slow, worshipful strokes.
He finally lets Izuku’s legs drop, shifting to loom over him again. His lips are wet, his chin glistening. He looks utterly feral, utterly satisfied. “Mine,” he breathes, leaning down to kiss Izuku deeply, letting him taste himself on Kacchan’s tongue. “Inside and out.”
Izuku kisses back, limp and boneless, the final barrier shattered. There is nothing of him that isn’t Kacchan’s. No part of Kacchan that isn’t now his. The circle is complete. He is full. He is empty. He is claimed.
The months bled together in a rhythm of work, warmth, and desperate, hopeful breeding. The clinic thrived in a way Izuku had never dreamed. Kacchan, with his low growls and steady presence, had an unnerving way of calming even the most terrified animals. He’d stand in a kennel with a shivering, aggressive terrier, murmur something in a language of rumbles and clicks, and the dog would still, whining softly before licking his hand. Word spread. Appointments booked out for months. The extra income was a tangible weight, a safety net that quickly became a down payment.
Their new house smelled of fresh paint and pine cleaner, a blank canvas they slowly stained with their own scent. Izuku’s old apartment, with its memories of rain and shocking transformation, was a closed chapter. Here, there was a yard. A real kitchen. A bedroom with a lock on the door and a bed large enough for Kacchan to pin him in any configuration they could dream up.
Which they did. Constantly. The desperate marathon of that first day never truly ended; it simply found a new tempo. A quick, rough taking against the kitchen counter before opening the clinic. A slow, deep claiming in the bath after closing. Wakeful hours in the dark where Izuku would arch his back and beg for Kacchan's knot, for the flood, for the impossible hope that was taking root in his mind. “Fill me up, Kacchan,” he’d gasp, fingers scrabbling at the headboard. “Please, I need it, need you to put puppies in me.”
Kacchan always obliged. He’d drive into him with a possessive snarl, locking them together, pumping him full until Izuku’s slender belly rounded slightly under the sheer volume. They’d lie there, knotted, Kacchan’s hand splayed over the faint swell. “Good,” he’d rumble, nosing at Izuku’s sweaty neck. “Taking my seed so good. Gonna breed you full.”
The hope became a quiet, shared obsession. Izuku tracked his cycles with a veterinarian’s clinical precision and a mate’s frantic hope. He bought the test on a Tuesday morning, the pharmacy aisle fluorescent and glaring. The box felt heavy in his hands. Final.
He waited until Kacchan was outside, checking the fence line he’d insisted on reinforcing. The bathroom in their new home was bright, sun streaming onto the clean tiles. Izuku’s hands shook as he tore the packaging. His heart wasn’t hammering—it was a still, dead weight in his chest. He followed the instructions with robotic focus, set the stick on the edge of the sink, and set a timer on his phone.
Three minutes. He paced the five steps to the wall and back. He counted the tiles. He tried not to think about the hollow ache of the last negative test, four weeks prior, and how Kacchan had just growled, flipped him over, and fucked him harder, as if effort alone could force biology to comply.
The timer chimed. A soft, innocuous sound that sliced through the room.
Izuku couldn’t move. He stared at the white stick from across the room. He saw the twin lines. Clear. Unmistakable. A plus sign. Positive.
A sound tore out of him—a ragged, punched-out gasp. Then a sob. He stumbled forward, grabbing the counter, his knuckles white. He picked up the test, holding it close to his face, as if his vision was lying. The lines didn’t fade. They were there. They were real. His legs gave out. He slid down the cabinet to the cool tile floor, the plastic stick clutched to his chest, and he cried. Great, heaving sobs that shook his entire frame.
He didn’t hear the back door slam. He didn’t hear the frantic footsteps pounding through the house. He was lost in the storm of it, in the terrifying, wonderful reality of the thing he’d ached for.
The bathroom door flew open with a crack, the knob embedding in the drywall. Kacchan filled the doorway, his chest heaving, ears flattened back, crimson eyes wild with alarm. The scent of his mate’s distress had pulled him across the yard like a hook in his gut. “Izuku!” His voice was a snarl, edged with panic. He saw him crumpled on the floor, face wet, and he was across the room in an instant, dropping to his knees. His hands framed Izuku’s face, rough thumbs smearing tears. “What’s wrong? Hurt? Who?”
Izuku could only shake his head, the sobs hiccuping in his chest. He tried to speak, but it came out a wet, incoherent garble. He thrust the hand holding the test between them, shoving it against Kacchan’s chest.
Kacchan looked down, confusion etching his fierce features. He took the plastic stick, holding it up. He stared. His brows drew together. He looked from the test to Izuku’s wrecked face, his own expression shifting from panic to dawning, slow comprehension. He knew what this was. Izuku had shown him the empty ones, explained the lines. “This…” Kacchan’s voice was hushed, gravel grinding to dust. “This means…”
“I’m not sad,” Izuku choked out, the words finally breaking through. He grabbed fistfuls of Kacchan’s shirt, clinging to him. “Kacchan, I’m not sad. I’m… I’m pregnant. It’s positive. We… you… I’m having your puppies.”
The silence that followed was absolute. Kacchan didn’t move. He stared at the test, then his gaze dropped to Izuku’s stomach, still flat beneath his soft t-shirt. His hand followed his eyes, sliding down Izuku’s chest, over his belly, his touch uncharacteristically gentle. A tremor ran through his fingers.
When he looked back up, his crimson eyes were blazing. Not with feral heat, but with something deeper, something awe-struck and terrifyingly vulnerable. A low, incredulous rumble started in his chest, building into a raw, triumphant sound that wasn’t quite a growl and wasn’t quite a laugh. “Mine,” he breathed, the word filled with a new, profound weight. “Ours.”
He crushed Izuku to him then, burying his face in the green curls at his neck. Izuku felt the shudder that went through the powerful body holding him. He clung back, his tears cooling on Kacchan’s skin. The sobs turned to helpless, joyous laughter.
Kacchan pulled back just enough to find his mouth. The kiss wasn’t desperate or claiming. It was slow. Deep. A seal. A promise. Izuku tasted salt and the familiar wildfire taste of his mate, and under it, the sweet, terrifying certainty of their future. When they broke apart, foreheads pressed together, Kacchan’s grin was all sharp, proud teeth. “Told you I’d breed you full,” he murmured, his voice thick.
Izuku laughed, a wet, happy sound. “You did.” He placed his hand over Kacchan’s, where it still rested on his stomach. “Two lines. Positive. Do you think more than one is in there?”
Kacchan’s grin widened, feral and ecstatic. He leaned in, nipping gently at Izuku’s lower lip. “Yes. Litter.” He kissed him again, soft this time, a reverent press. “My mate. My den. My puppies.” Each word was a stone laid in the foundation of their new life. He stood, pulling Izuku up with him, holding him close. The plastic test lay forgotten on the sun-warmed tile, its message received. The crying was done. The hoping was over. What grew now was real.
They ended up having two pups, their family complete and a happy ending achieved.