Izuku feels it first—a firm, undeniable pressure against the small of his back, right through the fabric of Katsuki’s jeans. He’s still slumped against his father’s chest, shuddering from the aftershocks, his mind a blank static. The pressure is insistent. Hot. He goes very still.

He turns his head, just enough to look over his shoulder. His father’s face is close, impassive, those sharp red eyes watching him. Izuku’s gaze drops, then flicks back up. “You’re…” he starts, his voice a wrecked whisper. “You’re hard.”

Katsuki doesn’t move. Doesn’t adjust. He just holds Izuku there, the hard line of his cock a brand against his son’s spine. “Yeah.”

“Why?” The word slips out, small and confused.

“Why do you think?” Katsuki’s voice is low, a gravelly rumble in his chest that Izuku feels everywhere. His arms are still locked around Izuku’s middle, possessive and solid.

Izuku swallows. His own body is a mess of slick heat and trembling exhaustion. “Because… of me?”

“You were shaking,” Katsuki says, his breath warm against Izuku’s ear. “Making those little noises. Soaked my fucking fingers. You think that doesn’t do anything?”

“But you’re my…” Izuku trails off, the word ‘dad’ sticking in his throat. It feels wrong now. A lie.

“I’m what?” Katsuki prompts, his tone dangerously even.

“Nothing.”

“Say it.”

Izuku squeezes his eyes shut. The pressure against his back seems to pulse. “You’re my father.”

Katsuki is silent for a long moment. The only sound is their breathing, out of sync. “And?”

“And that’s… that’s why it’s wrong.” Izuku’s voice cracks on the last word.

Katsuki’s hand slides up from Izuku’s stomach to his chest, splaying over his sternum. He can feel the frantic beat of Izuku’s heart. “Nothing about keeping you safe is wrong. Nothing about making you feel good is wrong. Your body tells the truth, Izuku. Listen to it.”

“My body is confused,” Izuku whispers, a desperate protest.

“It’s not confused.” Katsuki shifts, just slightly, and the deliberate grind of his erection against Izuku’s back is unmistakable. A rough, claiming friction. “It knows exactly what it wants. So does mine.”

Izuku’s breath hitches. The deliberate grind is still echoing through his bones. “What does it want?” he whispers, the question trembling in the air between them. “Your body. What does it want?”

Katsuki’s hand, still splayed over Izuku’s sternum, presses down slightly. A grounding weight. “It wants what it’s been listening to for the last ten minutes.” His voice is a dark, steady thing. “It wants the sounds you make. The way you shake. The proof that I can make you feel that good.”

“That’s not an answer,” Izuku says, a weak defiance. He feels raw, split open. The hard line of his father’s cock is an answer all its own.

“It’s the only one that matters.” Katsuki’s other hand comes up, fingers threading into the short hair at the nape of Izuku’s neck. Not pulling. Just holding. Possessing. “You think I’m some robot? You think I don’t feel anything when you come apart in my hands?”

Izuku shakes his head, a tiny, frantic motion. He doesn’t know what to think. The world has narrowed to this couch, to the heat at his back, to the scent of smoke and sweat that is purely his father.

“Tell me what you think it wants,” Katsuki commands, his mouth close to Izuku’s ear. His breath is hot. “Say it.”

Izuku’s throat works. He can’t. The words are too big, too real. They’ll make this real.

Katsuki waits. The silence stretches, taut. Then he shifts again, his hips rocking forward, and this time the friction is slower. Deliberate. A rough, unmistakable simulation. Izuku feels every thick inch through the denim.

A broken sound escapes Izuku’s lips. It’s not a moan. It’s a surrender.

“It wants to be inside,” Katsuki says, the words blunt and final, spoken directly into the shell of Izuku’s ear. “Where you’re hot. Where you’re wet. That’s what it wants.”

Izuku turns in his father’s lap. The movement is clumsy, desperate. He doesn’t think. He just moves, twisting until he’s straddling Katsuki’s thighs, their faces inches apart. The hard line of his father’s cock is now a burning pressure against his own stomach. Izuku’s hands come up, shaking, and frame Katsuki’s jaw. Then he kisses him.

It’s not graceful. It’s a messy press of lips, too hard, all teeth and panic and want. Izuku pours every confused, hungry thing inside him into it. He tastes salt—his own tears, or his father’s sweat. He doesn’t know.

Katsuki goes utterly still beneath him. For one terrifying second, Izuku thinks he’s made a catastrophic mistake. Then a low, rough sound vibrates in Katsuki’s chest, and his hands come up to grip Izuku’s hips, holding him in place. He doesn’t deepen the kiss. He lets Izuku lead, lets him explore the unfamiliar terrain of his father’s mouth with frantic, inexperienced swipes of his tongue.

Izuku breaks the kiss, panting. His lips feel swollen. His eyes are wide, searching Katsuki’s impassive face. “I want…” he breathes, the words sticking. His fingers fumble for the button of Katsuki’s jeans.

“Say it,” Katsuki says, his voice a graveled command. His thumbs dig into the soft flesh of Izuku’s hips.

“I want your cock.” The vulgarity feels alien in Izuku’s mouth, but it’s the only truth left. His fingers finally pop the button, drag the zipper down. The sound is obscenely loud in the quiet room.

Katsuki watches him, his crimson eyes dark, unreadable. He doesn’t help. He just leans back against the couch, giving Izuku room, letting him work. The denim parts, and the thick, heavy shape of him strains against the fabric of his briefs. Izuku’s breath catches. He hooks his fingers into the waistband of both layers and pulls them down, just enough.

His father’s cock springs free, thick and uncut, resting heavily against his stomach. It’s flushed dark, the head already wet. Izuku stares, his mouth dry. It’s massive. Intimidating. Beautiful. A primal part of him clenches deep inside, a wet, aching pulse of recognition.

“Nervous?” Katsuki asks, his tone flat. His hands are still on Izuku’s hips, a steady, anchoring heat.

“Yes,” Izuku whispers. He isn’t. Not really. The nervousness is a thin veneer over a deeper, surging confidence. This is what he’s dreamed of. What his body has been screaming for. He leans forward, his own weight settling more fully onto Katsuki’s thighs.

He doesn’t hesitate. He wraps a trembling hand around the base, feeling the hot, velvety skin, the powerful throb of a pulse beneath. He leans down further, his green curls brushing Katsuki’s stomach, and takes the head into his mouth.

The taste is musky, salt-bitter, purely male. It’s his father. Izuku moans around him, the vibration earning a sharp hiss from above. He sinks down, taking more, his jaw stretching. He’s never done this before, but his body seems to know what to do—his tongue exploring the slit, lapping at the pre-cum, tracing the thick vein on the underside.

“Look at you,” Katsuki murmurs, his voice thick. One of his hands leaves Izuku’s hip to thread into his hair, not forcing, just holding. “My good boy. Taking it so well.”

Izuku shudders at the praise, a fresh wave of slick heat gathering between his own thighs. He bobs his head, trying to take more, his nose pressing into the coarse hair at the base. He gags slightly, pulls back with a wet sound, then goes down again, more determined.

“Slow,” Katsuki instructs, his fingers tightening slightly in Izuku’s hair. “You don’t have to choke on it. Just taste it. Get used to it.”

Izuku pulls back with a wet pop, his lips slick and swollen. He looks up, his green eyes wide and dark in the blue television light. “I want to choke on it,” he breathes, the words raw and honest. “I want to gag on it. I want you to fuck my mouth, Daddy.” His hand is still wrapped around the base, feeling the throb. “I’ve had so many dreams. Of this. Of sucking your cock.”

Katsuki’s jaw tightens. The hand in Izuku’s hair flexes. “Dreams.”

“Every night,” Izuku whispers, leaning forward to press a clumsy, open-mouthed kiss to the leaking head. “Since we left her. You, in the gym. On the roof. Here. Always you.”

“Tell me.” Katsuki’s voice is a low rasp. His other hand finds Izuku’s cheek, thumb stroking over the damp skin. “What did I do in these dreams?”

Izuku shivers. He takes the tip back into his mouth, suckling gently, gathering the bitter-salt taste before he answers. “You fucked me,” he says around him, the vibration making Katsuki’s hips jerk. He pulls off again, a string of saliva connecting his lip to the glistening crown. “Hard. On a weight bench. You held me down and… and I begged for it. I woke up soaked. Every time.”

Katsuki watches him, his crimson gaze unblinking. “You begged.”

“Yes.”

“Beg now.”

Izuku doesn’t hesitate. The dream-logic has him, the confession has freed something. “Please,” he whispers, shifting on Katsuki’s lap, his own neglected arousal a throbbing ache. “Please, Daddy, fuck my mouth. Use me. I need it.”

A rough sound tears from Katsuki’s throat. The hand in Izuku’s hair tightens, guides him back down. “Open.”

Izuku obeys, mouth slack, tongue out. He looks up, maintaining eye contact as Katsuki feeds the thick head past his lips. Then his father pushes.

It’s not gentle. It’s a slow, inexorable invasion, stretching Izuku’s jaw, filling his mouth, pressing against the back of his throat. Izuku gags, his eyes watering instantly. He tries to relax his throat, breathing harshly through his nose.

“That’s it,” Katsuki murmurs, his voice strained with control. He holds himself there, buried to the hilt, letting Izuku feel the full, impossible stretch. “Take it. Just like you dreamed.”

He pulls back, almost all the way out, then thrusts back in, a little faster. Izuku gags again, tears tracking down his cheeks. It’s overwhelming. It’s perfect. The reality is hotter, thicker, more real than any dream. The musk and salt of his father’s skin is the only thing in the world.

Katsuki sets a rhythm, deep and punishing, each thrust punching a wet, choked sound from Izuku’s throat. His other hand grips Izuku’s shoulder, holding him steady. “Look at you,” he grunts, his hips pumping. “My boy. Taking his father’s cock so good. Dreamed of this, huh?”

Izuku can only make a guttural, affirmative noise around the fullness. Drool is dripping down his chin, onto his own chest. His hands clutch at Katsuki’s thighs, nails digging into the denim. His own hips are rocking helplessly, seeking friction against the rough fabric of his father’s jeans.

“You love it,” Katsuki states, watching the tears, the mess, the absolute surrender. He speeds up, the slap of skin joining the wet, rhythmic sounds. “You love choking on it. Don’t you?”

Izuku nods frantically, his throat working around the intrusion. The gagging is starting to fade, replaced by a dizzying, euphoric acceptance. This is where he belongs. Like this.

Katsuki’s breathing grows ragged. His thrusts become less controlled, more urgent. “Gonna come,” he warns, his voice a dark scrape. “Gonna fill that pretty mouth. You swallow every drop. That’s what you do in the dreams?”

Izuku moans, a desperate, hungry sound. He tries to nod again, his eyes pleading.

Katsuki’s control snaps. He buries himself deep, holds Izuku’s head in place, and groans—a raw, unfiltered sound of release. Izuku feels the hot, pulsing flood hit the back of his throat. He swallows convulsively, once, twice, the taste bitter and primal. He doesn’t let a drop escape.

When Katsuki finally softens and slips out, Izuku collapses forward, forehead resting on his father’s thigh, coughing weakly. His jaw aches. His face is a mess of tears and spit and come. He’s trembling violently.

Katsuki’s hand comes to rest on the back of his neck, heavy and warm. His own breathing is slowly evening out. For a long moment, the only sound is the quiet hum of the penthouse and Izuku’s ragged breaths.

“Dreams,” Katsuki says finally, his thumb stroking the damp hair at Izuku’s nape. “They’re just practice. This is real.”

Katsuki’s hand slides from Izuku’s neck to his shoulder, pulling him up and back. Izuku comes easily, boneless, letting himself be rearranged until he’s cradled sideways in his father’s lap, his cheek pressed against the solid wall of Katsuki’s chest. The aftershave and sweat and sex smell of him is everywhere. Katsuki’s arms wrap around him, tight and possessive.

“Look at me,” Katsuki says, his voice rough but quiet.

Izuku tilts his head up. His face is still wet. Katsuki looks down at him for a long moment, his crimson eyes scanning every detail—the swollen lips, the tear tracks, the absolute surrender. Then he bends and captures Izuku’s mouth with his own.

It’s not like the desperate, clumsy kiss Izuku initiated. This is slow. Deep. A claiming of a different kind. Katsuki licks into his mouth, tasting himself there, and Izuku whimpers, his hands coming up to clutch at his father’s shirt. The kiss is thorough, unhurried, a mapping of possession. It’s wet and hot and so fucking intimate Izuku feels dizzy.

When Katsuki finally breaks for air, he doesn’t go far. His forehead rests against Izuku’s. “You swallowed it all.”

“You told me to,” Izuku breathes, his lips tingling.

“I know.” Katsuki kisses him again, softer this time, a brush of lips. “My good boy.”

Katsuki kisses him again, a slow, thorough press of lips that tastes like salt and possession. He pulls back just enough to speak, his voice a low rumble in his chest where Izuku’s ear is pressed. “Bed. Now.”

Izuku nods, his body humming with a spent, liquid exhaustion. He doesn’t move. Katsuki’s arms tighten, then he shifts, standing in one fluid motion with Izuku cradled against him. Izuku lets out a soft gasp, his arms looping automatically around his father’s neck. He’s carried through the dark penthouse, past the blue glow of the silent TV, down the hall.

Katsuki shoulders into Izuku’s bedroom, doesn’t turn on the light. He lays Izuku down on the cool sheets, then strips off his own shirt and jeans in the dark, the silhouette of him broad and solid. The mattress dips as he climbs in, pulling Izuku back against his chest, skin to skin. His front is a wall of heat against Izuku’s back. One heavy arm wraps around Izuku’s waist, hand splaying possessively over his lower belly.

“You have that parent-teacher thing tomorrow,” Katsuki murmurs into the nape of his neck, his breath warm.

Izuku shivers. He’d forgotten. The real world feels like a distant, blurry photograph. “The conference. At three.”

“I’ll be there.” Katsuki’s thumb strokes a slow circle on his skin. “You nervous?”

“A little.” Izuku’s voice is hoarse from earlier. He swallows, his throat still tender. “What if they… ask about home?”

“They won’t.” Katsuki’s tone leaves no room for argument. “And if they do, they talk to me. That’s my job.” He presses a kiss to Izuku’s shoulder. “Your job is to sleep.”

Izuku closes his eyes. The darkness behind his lids is alive with the phantom sensation of fullness, of choking, of being used. His body aches in a dozen new, profound ways. The hand on his stomach is a brand. He’s never felt more claimed, or more terrified of what that means. “Daddy?”

“Hm.”

“Is this… are we sick?”

Katsuki is silent for a long moment. His hand stills. Then it slides lower, fingertips brushing the thatch of curls between Izuku’s thighs. Izuku jolts, a fresh pulse of wetness betraying him instantly. “Does that feel sick to you?”

Izuku shakes his head, a frantic little motion against the pillow. “No.”

“Then we’re not sick.” Katsuki’s fingers retreat, coming back to rest on his belly. “We’re us. This is what we are now. Your body knows it. Stop fighting it.”

A tear escapes, tracking hot into Izuku’s hairline. It’s a relief so deep it feels like drowning. “Okay.”

“Okay.” Katsuki nuzzles against him, his breathing beginning to even out into sleep. “Go to sleep, Izuku. I’ve got you.”

Izuku lets the weight of him, the scent of him, the impossible rightness of him, pull him under. The last thing he feels is the faint, steady thump of his father’s heartbeat against his spine.