The bed is clean, the damp towel from the bathroom abandoned on the floor. The afternoon light is heavy and grey, the rain still tapping a soft rhythm against the window. Izuku lies on his back, utterly spent, his body a map of tender places and phantom sensations. Kacchan is a solid, breathing weight along his side, one heavy arm thrown possessively across Izuku’s stomach, his nose buried in the crook of Izuku’s neck. Izuku thinks he should feel trapped. The arm is like an iron bar. Instead, the pressure grounds him, pulls him down into the mattress, into a exhaustion so complete it feels like drowning in warm syrup. His last thought is a vague, hazy wonder at how a creature of such violent claiming can also be the most solid, warm thing he’s ever held. Then, darkness.
He wakes to darkness, too, but of a different kind. The room is black, the lamp off, the only light a faint orange glow from the city streetlights filtering through the rain-beaded window. The tapping has stopped. The world is quiet, holding its breath. Izuku is on his side, curled inward, and he is surrounded by heat. Kacchan is wrapped around him from behind, big body spooning his smaller one, their legs tangled. Kacchan’s chest is a furnace against his back. The arm is still there, hooked low over his hip, a hand splayed possessively over the flat of Izuku’s belly. He can feel the soft puff of Kacchan’s breath against the nape of his neck.
His mind swims up from the depths, slow and thick. The events of the day—the bath, the marking, the taste, the shame, the shocking, undeniable pleasure—unspool in his head not as a narrative but as a series of physical echoes. His skin remembers every touch. His mouth remembers the salt-bitter taste. Between his legs, a familiar, low ache pulses, a sleepy throb of interest. He shifts slightly, and the hand on his stomach tightens, pulling him back flush against the hard line of Kacchan’s body. A low, rumbling sound vibrates through Kacchan’s chest and into his own spine. Not a growl. A purr.
“Kacchan?” Izuku whispers, his voice rough with sleep.
The purr deepens. The nose at his neck nuzzles, inhales. “Mine,” comes the sleep-rasped reply, the word slurred but absolute.
Izuku shivers. It should be terrifying. This feral man who urinated on his face, who holds him like he’s a prize. But the warmth is intoxicating. The possessiveness is a cage, but it’s a cage that feels, inexplicably, like safety. Like being known. He’s so tired of being overlooked. He turns his head, just an inch, and his lips brush the muscular forearm curled near his face. The scent there is overwhelming—ozone, musk, clean sweat, *Kacchan*. It goes straight to his head, makes his pussy clench empty and eager. He’s wet. Already. Just from waking up like this.
He turns fully in the circle of Kacchan’s arms, a slow, deliberate rotation until they’re face to face in the dark. He can just make out the sharp line of Kacchan’s jaw, the glint of crimson eyes watching him, alert now. Izuku doesn’t think. He leans in and presses his mouth to Kacchan’s.
It’s not like before. It’s not a claiming assault. It’s soft, questioning. A languid exploration of lips still slack from sleep. Kacchan goes still for a heartbeat, then his mouth opens under Izuku’s, and he takes over. The kiss deepens, turns hungry, but it’s a slow, thorough devouring. His tongue maps Izuku’s mouth, and Izuku meets it with his own, tasting the ghost of himself there. One of Kacchan’s hands comes up to cup the back of Izuku’s head, fingers tangling in the curls. The other slides down, over the curve of his ass, pulling their hips together.
The contact is electric. Izuku moans into the kiss, his body arching. He can feel the hard, thick length of Kacchan’s cock, still sheathed but pressing insistently against his lower belly. His own hips rut forward instinctively, seeking friction, and the slick heat between his thighs becomes a desperate, throbbing reality. He breaks the kiss, panting. “I’m… I’m all wet again. Already.”
Kacchan’s eyes burn in the dark. His hand leaves Izuku’s hair, trails down his neck, over the small, sensitive bud of his nipple, making Izuku gasp. “Good.” His voice is a gravelly scrape. “Means you’re ready.”
Izuku’s heart hammers against his ribs. He knows what ‘ready’ means. His mind flashes to the memory of that thick, red cock, the obscene bulge of the knot at its base. Fear flickers, a cold little dart. But it’s drowned out by a hotter, deeper need. The empty ache is unbearable. He wants to be filled. He wants the claim to be complete. He takes a shaky breath, his fingers tracing the hard line of Kacchan’s collarbone. “I… I want it.”
Kacchan goes preternaturally still. “Say it.”
“I want your knot.” The words leave his mouth, raw and honest. He feels Kacchan’s cock twitch against him, a violent jerk of reaction. Emboldened, terrified, he continues in a rush. “I want you to… to lock us together. Just… please. Go slow? You’re so… you’re really big, Kacchan.”
Kacchan’s answer is another kiss. It’s not soft. It’s deep, consuming, a seal of promise. His tongue pushes into Izuku’s mouth, claiming the space, and Izuku opens for him with a broken sigh. The hand on his ass moves, grips his thigh, and hauls it up and over Kacchan’s hip. In one smooth, powerful motion, Kacchan rolls them, settling his heavy weight on top of Izuku, caging him between thick thighs and the mattress. Izuku gasps into the kiss, his hands flying up to brace against the solid wall of Kacchan’s chest.
“Slow,” Kacchan rasps against his lips, the word a hot puff of air. It’s a vow. He grinds his hips down, and the thick, sheathed length of him drags through the slick mess between Izuku’s thighs, making them both shudder. “Gonna open you up first. Get you ready for me.”
Izuku nods, frantic, his head pressing back into the pillow. His heart is a wild drum against his ribs. He feels split open already, vulnerable under this heat and weight. Kacchan shifts, kneeling back to settle between Izuku’s spread legs. The loss of full contact is a cold shock, but then Kacchan’s hands are on his inner thighs, pushing them wider, his crimson eyes raking over the exposed, glistening flesh. Izuku wants to hide. He doesn’t. He lets himself be seen.
“So wet for me,” Kacchan murmurs, his voice thick. He leans down, not to kiss his mouth, but to drag his tongue over one of Izuku’s small, puffy nipples. Izuku cries out, back arching, the bud pebbling instantly under the rough, hot stroke. “All for me.”
“All for you,” Izuku whimpers, the truth of it shuddering through him. His fingers clutch at the sheets. “Just… please.”
Kacchan moves lower. His breath ghosts over Izuku’s belly, his hips, and then the hot, damp thatch of curls. Izuku holds his breath. A broad thumb strokes through his folds, gathering wetness, spreading it. The touch is deliberate, possessive. It makes Izuku’s toes curl. “Pretty cunt,” Kacchan says, the crude word a filthy, reverent prayer. “My pretty cunt.”
Then a finger, blunt and thick, presses at his entrance. Not pushing in. Just resting there, a threat and a promise. Izuku’s entire world narrows to that point of pressure. He’s so empty, so achingly ready, his body clenching around nothing. He looks down, meeting Kacchan’s burning gaze. “Kacchan…”
“Watch,” Kacchan commands, and Izuku obeys, propping himself up on his elbows. He watches as that single finger begins to sink into him, slow, so impossibly slow. The stretch is immediate, a bright, burning fullness. He’s tight, unused to this, and his body fights for a second before surrendering, sucking the digit deeper with a wet, yielding sound. Izuku moans, long and low, his head falling back. It’s not enough. It’s everything.
“You take it so good,” Kacchan growls, his eyes locked on where his finger disappears into Izuku’s body. He curls it, just slightly, and Izuku jolts, a sharp, surprised cry tearing from his throat. “There?”
“Y-yes—!” Izuku sobs, his hips jerking. The sensation is electric, a direct line to the throbbing knot of need in his core. Kacchan does it again, a slow, relentless press against that spot inside him, and Izuku’s vision whites out at the edges. His pussy flutters, dripping, clenching rhythmically around the invading finger. He’s already close, just from this. The realization is terrifying. He’s so sensitive, so ruined for anything else.
Kacchan adds a second finger. The stretch burns, a delicious, tearing ache. Izuku grits his teeth, a tear escaping down his temple. “Breathe,” Kacchan orders, his voice strained. He’s watching Izuku’s face, not his hand, reading every twitch, every flinch. He scissors his fingers gently, opening him wider, the wet sounds obscene in the quiet room. “That’s it. Take it. For me.”
Izuku forces a ragged breath into his lungs. The burn subsides, melts into a deep, throbbing fullness. He feels opened, vulnerable, his body yielding to the slow, patient stretch. Kacchan’s fingers are moving inside him now, a steady, penetrating rhythm, each thrust brushing that perfect, devastating spot. Pleasure coils, tight and hot, low in his belly. His clit aches, a swollen, neglected pulse against the seam of his lips.
He’s babbling, he realizes. “Feels… so full, Kacchan, please, I need— I’m gonna—”
Kacchan’s mouth is on him before Izuku can finish his babbling plea—not on his mouth, but lower, a hot, wet seal over his swollen, aching clit. Izuku shrieks, his back bowing off the bed. The tongue is broad, rough, and relentless, flicking over the sensitive bud with a precision that is absolutely inhuman. It’s too much. It’s everything. The coil in his belly snaps.
“K-Kacchan, I’m—I’m gonna—!” Izuku sobs, his hands flying to tangle in spiky blond hair, not to push away but to anchor himself as the world dissolves into white-hot sensation.
Kacchan hums, the vibration traveling straight through Izuku’s core, and sucks. Hard. Izuku comes with a broken scream, his body seizing. Wet heat gushes, not just from his clenching pussy but in a sudden, shocking flood that soaks Kacchan’s chin, his fingers still buried inside, the sheets beneath them. He squirts, the release violent and endless, milking Kacchan’s fingers through the pulsating waves.
“Good,” Kacchan rasps against his trembling thigh, lapping at the oversensitive flesh as Izuku twitches and whimpers through the aftershocks. “Mine.”
The two fingers inside him are joined by a third. The stretch is monumental, a burning, tearing fullness that has Izuku crying out again, but his body is pliant, loose from the orgasm, and it yields with a wet, giving sound. Kacchan scissors them slowly, opening him up, the stretch a bright, constant ache. “So open,” Kacchan murmurs, his voice thick with awe. “So ready for me.”
Izuku’s body moves before his mind can catch up, a desperate, fluid arching of his spine. His hands leave the sheets, fingers digging into the backs of his own thighs, and he pulls. His knees come up, wide, past his ears, folding his body nearly in half, exposing everything to the hungry crimson gaze above him. The position is obscene, vulnerable, his soaked pussy gaping open around the three stretching fingers. He feels the cool air on his most intimate parts, and the shame is a ghost, briefly, before it’s burned away by a hotter, more urgent truth. He needs. “Kacchan—please, please, I need it, I need your dick, fuck me, please—”
Kacchan’s fingers go still, buried deep. His eyes are molten, fixed on the ruined, glistening hole presented to him. “Say it,” he growls, the command a rough vibration in the air between them.
“Your dog cock,” Izuku whimpers, the words filthy and perfect on his tongue. He’s babbling, tears of frustration and want mingling with the sweat on his temples. “I need your huge dog cock in my pussy, I’m so empty, please, just fuck me, breed me, I’m your slut, your mate, please—”
The fingers withdraw with a wet, slick sound. Izuku cries out at the sudden emptiness, his hips jerking upward, chasing the loss. He watches, panting, as Kacchan kneels back, his own body a tense line of muscle and intention. The thick, red length of his cock is fully unsheathed now, jutting up from a thatch of blond curls, the base already swollen with the promise of the knot. It’s terrifying. It’s everything Izuku wants. Pre-cum beads at the tip, and Izuku’s mouth waters with a visceral, craving need to taste it again.
Kacchan grips himself, his fist pumping once, twice, spreading the slickness over the broad tapered head. He doesn’t speak. He shifts forward, the mattress dipping, and the blunt, hot crown of him nudges against Izuku’s stretched, dripping entrance. The pressure is immense, a solid, burning promise of more. Izuku’s breath hitches, his fingers tightening on his thighs, holding himself open.
“Fuck slow,” Izuku gasps, the words tearing from his throat raw and desperate. His hips buck up, trying to impale himself on that burning crown. “Just—just put it in. Now. I need it now, Kacchan, please, fuck me hard—”
Kacchan’s control shatters. A guttural snarl rips from his chest, and he drives forward.
The first inch is a white-hot brand. Izuku screams, his back arching off the bed, his fingers clawing at his own thighs. It’s too much, it’s not enough, it’s a splitting, burning stretch that feels like it’s tearing him in two. His body fights, clenching violently around the invading thickness, but Kacchan doesn’t stop. He pushes, a relentless, piston-like thrust that sinks another impossible inch deeper. The tapered tip gives way to the thicker shaft, and Izuku sobs, tears flooding his vision.
The burning stretch becomes a solid, tearing fullness as Kacchan sheathes the rest of his impossible length in one final, brutal thrust. Izuku’s scream shatters into a choked sob, his body bowing, every muscle locked. He’s impaled, split open, the thick canine cock burying itself to the hilt where the knot already swells against his stretched rim. The sensation is a white-hot brand of too much, and his body seizes, clenching in a violent, involuntary spasm. Then, with a ragged gasp, he squirts again, a hot gush that soaks their joined hips and the sheets beneath, his pussy fluttering wildly around the invading thickness.
“Fuck,” Kacchan snarls, the word ripped from him. He doesn’t pause. He pulls back, the drag a devastating friction, and slams home again.
The violence of it steals Izuku’s breath. Each piston-like drive is a claim, a punishment, a blessing. His hips are lifted off the mattress with the force, his fingers losing their grip on his thighs to claw at the sheets. “Yes—! More—! Hurts, it hurts so good, don’t stop, please don’t stop—” he babbles, tears streaming, his voice a broken wreck. The pain is a bright, clarifying fire, and the pleasure is the fuel feeding it. Every thrust grinds against that deep, perfect spot, and his body answers with another helpless flood, squirting around the pounding cock, the wet slap of skin filling the room.
Kacchan’s hands find his hips, fingers digging into the soft flesh hard enough to bruise, holding him down to take the force. His rhythm is relentless, feral, each snap of his hips driving the air from Izuku’s lungs. “Mine,” he grunts with every thrust. “My. Cunt.”
Izuku’s mind whites out. There is nothing but this: the crushing weight, the splitting fullness, the animal heat of the body claiming him. He is a vessel being filled, a territory being mapped by force. The shame is gone, burned away. All that’s left is a desperate, screaming need for completion. “Knot—!” he gasps, the word a plea. “Want it—feel it—please, Kacchan, I need it—”
“Gonna get it,” Kacchan promises, his voice strained, a raw scrape of sound. His thrusts are losing their rhythm, becoming harder, deeper, more desperate. The swollen base of his cock catches against Izuku’s entrance with every drive, a tantalizing, impossible stretch. “Gonna lock you on me. Keep you full.”
The thought is obscene. Perfect. Izuku sobs, his body trembling violently, a coil winding tight in his gut again. He’s coming apart, shattered by the fucking, remade by it. His own arousal is a river, a continuous, hot leak that mixes with the squirt, making every slide a slick, filthy dream. He can feel the knot, a firm, insistent pressure, threatening to pop past the ring of muscle that strains to accommodate it.
“Now,” Izuku begs, his vision swimming. “Do it now, I can take it, I’m yours, just—!”
Kacchan’s next thrust is different. It’s deeper, final. He grinds forward, burying himself completely, and Izuku feels the thick, bulbous knot press insistently against his rim. It burns, a stretching, tearing sensation that borders on true pain. He screams, his back arching. “Breathe,” Kacchan commands, his own body trembling with the effort to hold still. “Take it. For me.”
Izuku forces a shuddering breath. He pushes down, his body yielding, surrendering. There is a pop, a sudden, shocking give, and then an overwhelming, impossible fullness as the knot slides home, locking them together. He is stuffed, complete, every internal inch claimed.
A broken, gasping cry leaves him. His pussy convulses, clamping down on the trapped thickness, and he comes. He squirts, a hot, gushing rush that soaks the sheets beneath them like a broken hose, his body wringing itself tight around the knot, milking it.
Kacchan shouts, a raw, animal sound, and his hips jerk. Heat floods Izuku’s core, a pulsing, endless rush as Kacchan comes inside him, filling him. The sensation triggers another wave, and Izuku squirts again, a weak, delirious trickle, his body spent and trembling. Kacchan collapses forward, catching his weight on his elbows, his forehead pressed to Izuku’s, their panting breaths mingling. He is locked inside, bound to him. Izuku can feel every twitch, every pulse of the cock buried in his belly.
“Mine,” Kacchan murmurs, the word a satisfied rumble against his skin. His tongue swipes over Izuku’s tear-streaked cheek. “All mine.”
Izuku can only nod, his limbs liquid, his mind a quiet, hazy static of fulfillment. The burning has faded to a deep, throbbing ache, the knot a constant, heavy presence. He is claimed. He is bred. The emptiness is gone, replaced by a weight that feels like home.
Kacchan’s hips shift, a slow, deliberate grind that makes the knot inside Izuku pull and press deeper. Izuku gasps, his oversensitive walls fluttering around the thick intrusion. More heat pulses into him, another fresh rush of cum filling the already flooded space. “Breeding you,” Kacchan rasps, his forehead still pressed to Izuku’s, his breath hot and ragged. “Finally. My mate. Full of me.”
Izuku’s head is swimming, a hazy, blissed-out float. He can feel it—the incredible stretch, the heavy, liquid warmth spreading inside his belly. A soft, delirious laugh bubbles out of him. “So much,” he slurs, his voice wrecked. “You’re filling me up so much, Kacchan. I can feel it… I’m gonna be dripping with you for days.”
“Good.” Kacchan nips at his bottom lip, a possessive punctuation. He grinds again, a circular motion that makes Izuku whine. “Marking you inside. Where it counts.”
“I love it,” Izuku babbles, the truth spilling out raw and unfiltered. His hands come up to clutch at Kacchan’s trembling shoulders. “I love your knot, I love your stupid, huge dog cock splitting me open, I need it, I need so much more, please, don’t ever stop breeding me—”
Kacchan’s growl is pure satisfaction. He licks a stripe up Izuku’s cheek, catching the salt of sweat and tears. “Mine to breed. Mine to knot. Whenever I want.”
“Whenever you want,” Izuku echoes, dazed and earnest. His pussy gives a weak, involuntary clench around the pulsing shaft, and another trickle of his own release mixes with the mess between them. The veterinary part of his brain, distant and foggy, supplies a fact: the knot will take time to subside. They’re locked like this. The thought doesn’t bring panic. It brings a profound, trembling peace. He is literally, physically unable to be separated from the source of his claiming. A perfect, biological bond.
“Gonna keep you,” Kacchan murmurs, his voice dropping into a rough, almost sleepy register. His weight settles more fully atop Izuku, a heavy, comforting pressure. “Always. In my den. My good mate.”
The warmth inside Izuku shifts. It’s no longer just the thick, pulsing heat of Kacchan’s release. It’s a new flood, a distinct, spreading pressure that feels hotter, more liquid. Izuku’s eyes fly open, his breath catching in his throat. He knows this sensation. His veterinarian’s mind, hazy with pleasure, identifies it a second before Kacchan growls the truth against his neck. “Marking you. Deep.”
The stream is a continuous, impossible heat, filling the space his cum already occupied, pressing outward. Izuku’s belly tightens, then begins to swell. A soft, punched-out sound escapes him. “K-Kacchan…”
“Mine,” Kacchan rasps, his arms tightening like bands of iron around Izuku’s back. His hips give a minute, possessive grind, ensuring the knot seals everything inside. “All of it. Stays in you.”
Izuku can only whimper, his hands sliding down from Kacchan’s shoulders to press against his own lower stomach. The flesh is firm, then soft, then firm again as it distends under the relentless internal flood. It’s a profound, weighty fullness that goes beyond anything he imagined. His pussy, already stretched to its limit around the knot, flutters weakly, overstimulated and accepting. He feels bloated, claimed in a way that is terrifyingly biological. His mind whites out, reduced to the sensation of being filled beyond capacity. A low, continuous moan vibrates in his chest.
“Look,” Kacchan commands, his voice rough with satisfaction. He shifts his weight slightly, just enough for Izuku to glance down the length of their joined bodies.
The sight steals the air from his lungs. His normally flat, freckled abdomen is rounded, a soft, obvious curve pushing outward. It’s taut, skin stretched shiny in the lamplight. He looks… he looks bred. Pregnant with Kacchan’s claim. The visceral wrongness of it—the sheer, impossible volume—collides with a wave of such dizzying, submissive need that he sobs. “Oh, god.”
“Good?” Kacchan nips his earlobe, a sharp, grounding punctuation.
“Y-yes,” Izuku chokes out, his fingers splaying over the swollen curve. It’s warm. He can feel the liquid weight inside shift as he breathes. “So full, Kacchan. I’m so full of you.” The words are a reverent whisper. The last of his clinical detachment dissolves. This isn’t anatomy. This is magic. This is ownership written in his very cells.
The internal stream finally eases, then stops. Kacchan lets out a long, shuddering sigh, his entire body going heavy and lax atop Izuku. The knot remains, a firm anchor keeping the immense pressure sealed within. Izuku feels impossibly heavy, weighted to the bed, his belly a hot, rounded burden that is also a prize.
“Sleep now,” Kacchan murmurs, his voice already slurring with exhaustion. He nuzzles into the crook of Izuku’s neck, his breath evening out. “Den. Sleep. My full mate.”
Izuku wants to respond, but his body is shutting down, overwhelmed by the cascade of sensation and the deep, biological peace of the bond. His hand stays on his stomach, a possessive mirror of Kacchan’s own claim. The lamp casts their tangled, wet shadows on the wall, a still life of utter completion. His last conscious thought is a quiet, searing truth: he is a vessel, and he is full, and he has never been more himself.