The headboard tapped against the wall. A slow, insistent rhythm. Thud. Pause. Thud. Izuku lay frozen, eyes wide in the dark, every muscle locked tight beside Shoto’s sleeping form.
Another thud. A low, muffled groan filtered through the plaster. Uncle Kacchan’s voice, strained and thick. Izuku’s own hand was a trapped animal under the quilt, fingers curled into a fist so tight his knuckles ached.
Thud. Thud-thud. Faster now.
Izuku’s breath hitched. The sound was a physical thing. It traveled through the wall, through the floor, and straight into the base of his spine. A hot, shameful pulse answered between his legs. His small, clean-shaven pussy clenched, empty and aching.
He could hear the bedsprings. The shift of weight. A sharper, wetter sound. Then his uncle’s voice again, a ragged, gritted-out curse. “Ei—fuck—”
Izuku’s hips gave a tiny, traitorous jerk against the mattress. He squeezed his eyes shut. He shouldn’t be listening. He shouldn’t be imagining the scene in the other room—Katsuki’s powerful body moving, driving into his husband, that large, girthy cock sheathing itself—
A sharp, broken moan. Uncle Kacchan. Coming.
The silence that followed was worse. It rang in Izuku’s ears. His own body was screaming. His nipples were hard, pebbled points against his soft sleep shirt. Heat flooded his thighs. He was wet. He could feel it. A slick, unmistakable soak.
Slowly, as if pulled by a string, his trapped hand uncurled. His fingertips brushed the cotton of his boxers. He flinched.
Shoto murmured in his sleep, turning onto his side. His back was to Izuku now. The perfect, princely line of his shoulder was a rebuke.
Izuku’s hand moved. It slid under his waistband. His own touch was a shock—too hot, too knowing. His fingers found the swollen, sensitive flesh. He was so wet his fingertips slid through his folds without resistance. A silent, shuddering breath escaped him.
He touched himself, listening to the heavy silence in the guest room, his own touch a guilty, perfect mirror of the lust that had just shaken the wall.
The silence broke with a soft, pleading whine from the other room. "Kats... come on, baby. One more time. Please." Eijiro's voice was thick, slurred with sleep and want.
"You're insatiable," Katsuki's voice rumbled back, low and rough. The bedsprings groaned.
"Your fault. You got me all worked up. Need you again. Need that big cock in my boy pussy." Eijiro’s words were a clear, shameless whisper through the wall. "Fuck me like you mean it. Like you own it."
Izuku’s breath stopped in his throat. *Boy pussy*. The crude, possessive term sent a jolt through him, a direct line of heat to his own cunt. It clenched, empty and soaking, a traitorous echo.
"You think you can take it?" Katsuki’s tone was a dark challenge. "You were crying earlier."
"Made me cry. Do it again. Wanna feel you tomorrow." The bed frame gave a metallic creak, then began a slow, deliberate rock against the wall. Thud. Thud.
Izuku’s hand, still tucked under his waistband, was paralyzed. His fingertips rested against his slick folds, burning with inaction. Each thud was a punctuation to the filthy, whispered conversation. His uncle’s husband was begging for it. Begging for *Kacchan’s* cock.
"Say it." Katsuki’s command was a guttural growl.
"Yours," Eijiro gasped, the word hitching with the rhythm. "My boy pussy is yours. All yours, Kats. Fuck—"
The rocking increased. Not frantic. Deep and measured. Powerfully sure. Izuku could almost see it—the shift of muscle, the sweat-slicked skin, the brutal, claiming pace. His own hips lifted off the mattress, a silent, desperate mimicry.
His fingers moved. A shallow, experimental circle around his swollen clit. Lightning. His jaw clenched to trap a moan. Shoto slept on, his breathing deep and even, a world away.
"Harder," Eijiro begged, voice breaking. "Fill me up. Wanna feel you cum in me."
Katsuki’s answer was a brutal, driving series of thrusts that made the headboard slam. The wall vibrated against Izuku's shoulder. He pressed his face into his pillow, his own touch deepening, circling faster, slick with his own wetness. He was fucking himself on his own hand, mirroring the rhythm through the plaster.
"Gonna come," Eijiro sobbed, the sound raw and real. "Kats, I'm gonna—"
"Do it." Katsuki’s voice was pure gravel, stripped of everything but feral approval. "Cum on my cock. Now."
A shattered cry, then a low, continuous groan. The slapping rhythm lost all coordination, becoming a messy, driving force. Izuku’s body coiled, a spring wound too tight. He was right there, teetering on the edge, listening to a stranger’s climax push him toward his own.
The memory hit him like a physical blow—the shower, the ice water, the shocking, unprecedented release. He couldn’t. Not here. Not with Shoto sleeping inches away, not with the evidence soaking his boxers. Izuku’s hand jerked back from his cunt as if burned.
He slid from the bed in one frantic, silent motion. The floorboards were cold under his feet. He didn’t look back at Shoto’s sleeping form. He just fled, shutting the bedroom door behind him with a soft click and stumbling down the dark hall to the bathroom.
He locked the door, leaned against it, and gasped. The air smelled faintly of bleach and his own sweat. Streetlight bled through the frosted window, painting the tub in weak stripes of gray. He shoved his boxers down his thighs, letting them pool at his ankles. The cool air hit his wet skin, making him shudder.
He didn’t make it to the tub. He sank to the floor right there, his back against the cold tile, knees falling open. His fingers found his clit again, swollen and throbbing. He flicked it, hard and fast, the way he had in the shower. No gentle circles now. This was punishment and release.
“Fuck,” he whispered into the empty room, the crude word a shock on his tongue. His hips jerked up off the tile, chasing the sharp, bright pain-pleasure of his touch. He was so close, a live wire about to snap. He pictured it—his uncle’ raw, commanding voice, the sheer power in his thrusts. The image coiled his stomach tight.
The orgasm tore through him, silent and violent. His back arched off the cabinet, his mouth open in a soundless scream. It wasn’t a peak, but a floodgate breaking—a hot, gushing release that soaked his thighs and the tile beneath him. He squirted, heavily, helplessly, pulses of it hitting the floor with soft, wet sounds. He rode it out, trembling, until he was spent and hollow.
He slumped, panting, staring at the glistening puddle between his splayed legs. Shame, hot and immediate, followed the physical cold. He’d done it again.
A firm, deliberate knock on the door made his heart stop.
“Occupied,” Izuku croaked, scrambling to grab a hand towel from the rack, pressing it between his legs.
“It’s me.” Katsuki’s voice was low, stripped of its usual bark. It was just a rumble through the wood.
Izuku froze. “I’ll—I’ll be out in a minute.”
“Open the door, Izuku.”
“Uncle Kacchan, I’m not decent—”
“Now.” The single word brooked no argument. It was the same voice that had commanded Eijiro to come.
Izuku’s hands shook as he fumbled with the lock. He pulled the door open just a crack, hiding his bare legs and the soaked towel behind it. Katsuki stood in the shadowed hallway, shirtless, wearing only a pair of low-slung sweatpants. His chest was damp with sweat, his hair mussed. He smelled like sex and salt.
His crimson eyes didn’t go to Izuku’s face. They dropped, taking in the discarded boxers around his ankles, the towel clutched at his thighs, the damp patch on the floor just visible behind the door. His jaw tightened. A muscle ticked in his cheek.
“Couldn’t sleep?” Katsuki asked, his voice dangerously quiet.
Izuku’s throat closed. He couldn’t speak. He just stared, caught.
Katsuki’s gaze finally lifted, meeting his. The heat in them was not familial. It was recognition. “Thin walls,” he said, the words a blunt, shared confession.
"You heard me?" Izuku whispered. The words hung in the humid bathroom air, a fragile, shameful bridge between them.
Katsuki didn’t move. His crimson eyes held Izuku’s, unblinking. "Every whimper," he said, his voice low. "Every choked-off breath.”
A hot flush crawled up Izuku's neck. He tightened his grip on the damp towel. "I didn't— It wasn't—"
"Don't." Katsuki’s gaze dropped again, slowly, deliberately tracing the line of the towel, the exposed skin of Izuku’s inner thighs, the glistening evidence on the tile. "Lie to me. I heard what you did. Saw the proof." He leaned one broad shoulder against the doorframe, blocking the hall. "Sounded like you were drowning."
Izuku’s breath hitched. "You should go back to your husband."
"Eijiro’s asleep. Came out for water." Katsuki’s eyes flicked to the sink, then back to Izuku. "Found something thirstier."
"Stop it."
"Stop what?" Katsuki pushed off the frame, taking one step into the bathroom. The space shrank instantly. Izuku could feel the heat radiating from his bare chest. "Naming it? You were on the other side of that wall, listening to me fuck my husband. You got so wet you had to run in here and make a mess on the floor." His voice dropped to a rough whisper. "My nephew is acting like a little slut."
Izuku shook his head, a frantic, wordless denial. He tried to shut the door, but Katsuki’s foot was there, a solid barrier.
"Look at it," Katsuki commanded, his tone leaving no room for refusal. He nodded toward the puddle on the tile.
Izuku’s eyes burned. He couldn’t look. "Please."
"Look."
Izuku looked. The streetlight caught the slick patch, making it shine. His own release. His shame, displayed.
"That came from you," Katsuki said, not a question. A fact.
"I was thinking about Shoto," Izuku choked out, the lie thin and desperate.
Katsuki’s laugh was a short, harsh puff of air. "Bullshit. You think about the boy sleeping down the hall, you don't end up squirting on the bathroom floor the minute I finish. That's a different kind of hunger." He leaned in, his voice a graveled scrape against Izuku’s ear.
Izuku’s hands flew up, palms slamming against Katsuki’s sweat-damp chest. The shove was weak, frantic. “Stop teasing me, Uncle Kacchan!”
Katsuki didn’t resist. He let the push move him back a single step, just enough for Izuku to swing the bathroom door shut. The lock clicked, a frail, final sound.
A low chuckle filtered through the wood. “Sleep tight, nerd.”
Izuku stood trembling, his back pressed against the door, listening to the heavy, retreating footsteps down the hall. He slid down to the cold tile, the damp towel still clutched in his fist. He sat there until his breathing slowed, until the heat in his face faded to a sickly chill.
He cleaned the floor with a vicious, shameful focus, scrubbing until the tile shone. He washed his hands three times. He avoided his own eyes in the mirror.
The hallway was dark and silent. He crept past the closed door of the guest room, heart hammering, but heard nothing. Back in his own bedroom, the streetlamp painted Shoto’s sleeping form in soft silver. He lay on his side, back to Izuku, his breathing deep and even.
Izuku slipped under the covers, the sheets now feeling like a lie. He stared at the solid line of Shoto’s shoulders, the way his red-and-white hair fanned across the pillow. The guilt was a physical weight on his chest.
He’d just settled, forcing his eyes shut, when the headboard in the next room tapped the wall again. A single, testing bump. Then another.
Izuku went rigid. A muffled, sleepy grumble came through the wall—Eijiro’s voice, thick with sleep. “Kats… c’mon, it’s late.”
“Go back to sleep,” Katsuki’s reply was a husky murmur, but the wall carried it perfectly. “Just getting comfortable.”
The rhythmic tapping began in earnest, slower this time, a deliberate, grinding drag of wood against drywall. A soft, punched-out moan followed. Eijiro’s.
Izuku bit his own knuckle, his eyes wide open in the dark. Other hand keeping still on his chest. He can't touch himself again, no matter how bad he wants to.
“You’re insatiable,” Eijiro sighed, the sound fond and exhausted.
“You love it,” Katsuki rasped, and the headboard’s tempo increased, a steady, pounding claim. “Take it. That’s it.”
The headboard’s rhythm became a brutal, driving staccato. Eijiro’s moans, muffled by the wall, were soft, surrendering things. Katsuki’s voice was a guttural chant. “Yeah. There. C’mon.”
Izuku squeezed his eyes shut so tight he saw sparks. His free hand fisted in the sheets. The other stayed, trapped and guilty, on his sternum. He held his breath, muscles locked, as the sounds crested—a choked cry, a low, satisfied groan, the final, shuddering impact of wood against drywall.
Silence.
It was worse than the noise. It was an arena for his heartbeat, a frantic drum against his ribs. He listened for whispers, for the rustle of sheets, for anything. Nothing came.
“Kats?” Eijiro’s voice was a slurry, sleepy mumble.
“Sleep, Ei.” Katsuki’s reply was rough, spent. “Told you I just needed to get comfortable.”
A soft, affectionate grunt. Then genuine quiet.
Izuku unclenched his jaw. He let out a slow, trembling breath. The heat between his legs was a dull, shameful ache. He focused on the solid line of Shoto’s back, the steady rise and fall under the blanket. He counted them. One. Two. Ten.
Sleep did not come. It hovered, a taunt just out of reach. Every time his thoughts stilled, the memory of the bathroom floor flashed behind his eyelids—the slick tile, Katsuki’s voice naming his shame. His body would tense again, a fresh wave of heat prickling under his skin.
The streetlamp outside cast the room in long, blue shadows. He watched them creep across the ceiling. He listened to the house settle—a pipe groaning, the faint hum of the refrigerator downstairs. Normal sounds. They felt like accusations.
Shoto shifted in his sleep, turning onto his back. His face, serene in the dim light, was turned toward Izuku. The perfect line of his nose, the soft part of his lips. Izuku’s chest tightened with a love so sharp it felt like grief.
He reached out, his fingers hovering just above Shoto’s cheek. He didn’t dare touch. His hand was the same hand that had been on the cold tile. It felt filthy.
“I’m sorry,” Izuku whispered into the dark, the words soundless.
Dawn was a grey smear at the window when exhaustion finally pulled him under. His sleep was thin and fractured, filled with the sound of tapping wood and the scent of his own musk on a clean, white towel.