The foyer's marble floor was a glacier under Katsuki's sneakers, the air thick with some cloying, floral perfume that didn't belong. It smelled like invasion. He dropped his bag, the thud echoing in the vaulted space, and didn't turn to look at the girl trailing him. Camie. Her name was Camie.

"Your house is, like, insane," she breathed, her voice all airy awe. She was already touching the banister, her fingers skimming the polished wood. "It's so clean."

"Shut up," Katsuki muttered, his crimson eyes scanning the shadowed archways leading to the kitchen, the living room. Dark. Quiet. "Mom's asleep. Keep your voice the fuck down."

"Aww, you're being all secretive." She sidled up to him, pressing her chest against his arm. "It's kinda hot. Bad boy bringing a girl home to fuck while Mommy's upstairs."

He looked down at her, a slow, predatory smirk pulling at his mouth. His hand came up, rough fingers tangling in her hair and tilting her head back. "You talk too much." He wasn't thinking about her. He was thinking about the silence upstairs, the particular quality of it when his mother was truly asleep. This was a challenge thrown into that silence. A offering. "You wanna fuck or not?"

In the dark mouth of the formal dining room, unseen behind the heavy curtain of the archway, Izuku stood perfectly still. The cold marble seeped through his slippers. His green eyes, wide and unblinking, tracked the silhouette of his son against the faint streetlight bleeding through the fanlight. Camie's perfume was a vulgar stain in his foyer, in his air. His nostrils flared. He watched Katsuki's hand, the one he knew every callus and scar of, fist in that cheap blonde hair.

"Yeah," Camie giggled, the sound like breaking glass to Izuku's ears. "Show me how bad you are, Katsu."

Katsuki’s smirk sharpened, a blade in the low light. He didn’t let go of her hair. “Tits out. On your knees.”

Camie’s breath hitched, a sound of pure excitement. “Okay, bad boy.” She scrambled, fingers fumbling with the buttons of her blouse. The fabric fell open. She shimmied out of it, then knelt on the cold marble, her bare skin pebbling. She looked up at him, all wide eyes and parted lips. “I’ve heard the stories. Let me see it.”

“You don’t get to see shit until I say.” His voice was a low growl, a performance for the sleeping house. He undid his belt, the leather sliding free with a whisper that echoed. His zipper was louder. He pushed his pants and boxers down just enough, freeing his cock. It was already half-hard, thick and heavy in the dim light. Camie gasped, a real one this time.

Izuku’s fingernails bit into his own palm from the archway. That. That monster. The one he’d diapered, bathed, watched grow. It was obscene. It was beautiful. A part of him, out there in the open, being looked at by this… this stain. His breath came shallow, silent. He watched Katsuki grasp himself, giving a rough, slow stroke. Pre-cum beaded at the tip, gleaming.

“Holy shit,” Camie breathed, reaching out.

Katsuki tapped her cheek with the hot, wet head. “Not yet. Tits together.”

She obeyed instantly, pressing her breasts together, creating a soft, warm valley. Katsuki stepped forward, the marble cold under his feet. He guided his cock between them, the heat of her skin making him hiss. He looked down, his crimson eyes glinting, but his gaze flickered past her, toward the dark stairwell. “Gonna fuck the shit out of these,” he muttered, and began to move.

The sound was wet, intimate. A slick, rhythmic slide. Camie’s soft moans filled the foyer, mixing with Katsuki’s ragged breaths. Izuku watched, unblinking. Every thrust was a violation of his home, a theft. That was his boy. His. His throat tightened. A familiar, aching heat pooled low in his own belly, a traitorous pulse between his legs. He hated her. He hated the way Katsuki’s abs clenched, the way his jaw was set in that focused, brutal line.

“Fuck, Katsu, you’re so big,” Camie whimpered, trying to crane her neck to watch.

“Shut up and hold still,” Katsuki grunted, his pace increasing. The slap of his hips against her chest was a sharp, staccato beat in the silent house. He wasn’t looking at her face. His eyes were closed now, head tilted back slightly, as if listening for something else.

Inside the dining room’s darkness, Izuku’s hand moved. Slowly, silently. It slipped beneath the waistband of his soft sleep pants. His fingers, the ones that kneaded dough and smoothed Katsuki’s hair, found his own soaked cunt. He was dripping. The slickness shocked him, even now. He pressed two fingers inside himself, a sharp, silent gasp escaping his lips. It was wrong. It was the only thing that felt right. He matched the rhythm from the foyer, his own hips rocking minutely against his hand. He watched his son fuck, and he fucked himself on his own fingers, his other hand clamped over his mouth.

Katsuki’s movements became rougher, more frantic. “Gonna cum on your face,” he snarled, the words garbled. “Swallow every fucking drop.”

“Yes, yes, please—” Camie babbled.

Izuku’s fingers curled, stroking that deep, desperate spot inside him. His vision blurred. He was close. So was Katsuki. He could tell by the hitch in his boy’s breath, the way his thrusts lost their rhythm. This was it. The offering. The defiance. The proof that Katsuki was his, no matter whose tits he used. Izuku’s back arched against the wall, a silent scream building in his chest as he felt his own climax tear through him, hot and shameful and perfect, just as Katsuki groaned above the kneeling girl.

Izuku watches, breath held, as his son’s release paints the girl’s upturned face. Thick, pearlescent streaks land on her cheeks, her lips, her eyelids. Katsuki’s groan is a raw, spent thing that vibrates in the foyer’s hollow air. A fierce, unspeakable ache claws behind Izuku’s teeth. He wants to be the marble floor, to catch it. He wants to be the girl’s stupid, open mouth, to swallow it. He wants to lick it from his baby boy’s still-throbbing cock himself, to taste the salt and heat and proof of him, to have that monster spill down his own throat where it belongs.

“Good girl,” Katsuki rasps above Camie, the words hollow, automatic. He’s already pulling back, tucking himself away with a grimace of distaste. He doesn’t look at her face, at his own mess on it. He zips his jeans, the sound definitive. “Clean yourself up. The bathroom’s down the hall. Don’t use the good towels.”

In the dark, Izuku slowly withdraws his slick fingers from himself. The shame arrives then, cold and slick, washing over the fading heat in his belly. He wiped Kacchan’s chin once, just like that. He pressed kisses to scraped knees. His hands, now trembling and wet, had made his son’s birthday cake last week. He felt filthy. He was filthy. He wanted to do it again the next time Katsuki brought a stain home.

Camie sat back on her heels, wiping at her eyes with the back of her hand. “Wow,” she giggled, voice shaky. “You really are a monster.”

The heavy curtain of the dining room archway stirred. Izuku stepped into the faint light of the foyer, rubbing one eye with a knuckle, the picture of sleep-addled confusion. His green curls were mussed, his sleep pants soft and rumpled. He blinked slowly at the scene before him: his son, Katsuki, standing with his back to the stairwell, and a half-naked girl on her knees, a glistening, pearlescent mess on her face.

“Kacchan?” Izuku’s voice was a soft, sleep-rough murmur. “What’s all this noise, baby boy? I thought I heard something.”

Katsuki went rigid. His crimson eyes, which had been dull and dismissive a second before, sharpened instantly, locking onto his mother. A flicker of something—panic, defiance, a weird, possessive pride—crossed his face before it smoothed into his usual bored mask. “Mom. The fuck are you doing up?”

Izuku padded forward, barefoot on the cold marble, ignoring the girl completely. He reached up and cupped Katsuki’s cheek, his thumb stroking just under his son’s eye. “I woke up and you weren’t in your room. I got worried.” His touch lingered, intimate and proprietary. “You know I don’t sleep well when you’re not home.”

Camie stared, wiping sluggishly at the cum on her chin. “Who the hell is this?” she blurted, her voice too loud in the tense quiet.

Katsuki’s reaction was instantaneous. He moved so fast he was a blur. He stepped between Izuku and Camie, his broad back blocking her view. His hand shot out, not to hit her, but to grip Izuku’s waist, pulling his mother closer to his side in a gesture that was blatantly, defensively possessive. “Watch your fucking mouth,” he snarled, the sound low and vicious. “That’s my mom.”

“Your… mom?” Camie’s eyes widened, darting between Izuku’s slender, freckled frame and Katsuki’s protective, towering anger. “But he’s a—”

“He,” Katsuki cut her off, his voice dropping to a deadly, quiet register. “Is my mother. You got a problem with that?” His fingers tightened on Izuku’s hip, his knuckles white. “You say one more wrong thing about him, and you won’t walk out of here.”

Izuku leaned into the hold, tilting his head to rest his temple against Katsuki’s bicep. He smiled up at his son, a soft, approving curve of his lips. “It’s alright, Kacchan. She’s just confused.” He finally let his green eyes slide to Camie, and the warmth drained from them, leaving something flat and assessing. “You should go clean up, sweetheart. The bathroom is just down the hall. Like my boy said.”

The dismissal was absolute. Camie scrambled to her feet, clutching her blouse to her chest. She looked from Katsuki’s murderous glare to Izuku’s placid, eerie smile, and a shiver ran through her that had nothing to do with the cold floor. “I… yeah. Okay.” She scurried away, her footsteps echoing toward the guest bath.

The moment she was gone, the air in the foyer changed. The performance dropped. Katsuki’s grip on Izuku’s hip didn’t loosen; it shifted. His thumb began to rub slow, absent circles through the thin fabric of Izuku’s sleep pants. He was still breathing hard from the confrontation, from the sex, his chest rising and falling against Izuku’s side. “You shouldn’t have seen that,” he muttered, not looking at him.

“Seen what, baby?” Izuku whispered, his hand coming up to splay over Katsuki’s pounding heart. He could feel the frantic beat under his palm. “I just saw my boy defending his mommy. That’s all.” He pressed closer, his nose brushing the column of Katsuki’s throat. He could smell it now, over the cloying perfume: the salty, musky scent of his son’s release. It made his head swim. His own cunt, already sensitized and slick from earlier, gave a treacherous, aching throb.

Katsuki swallowed hard. His other hand came up, fingers threading into Izuku’s green curls, not pulling, just holding. He rested his cheek against the top of his mother’s head. His voice was a raw whisper, meant only for the space between their bodies. “She was nothing, Mom. Just… nothing.”

“I know, Kacchan,” Izuku breathed, turning his face into Katsuki’s neck. He inhaled deeply, drowning in the scent of caramel, clean sweat, and sex—his son’s sex. His lips brushed the hot skin there, a ghost of a kiss. “Mommy knows.”

Izuku’s lips, still curved in that soft smile, press against Katsuki’s mouth. It’s a deep, lingering kiss, the kind a mother shouldn’t give her grown son. His tongue slips past the seam of Katsuki’s lips for a second, tasting the leftover aggression, the sharpness of his breath. Katsuki freezes for a heartbeat, then his hand in Izuku’s hair tightens, and he kisses back, hard and possessive, a silent battle for control in the foyer’s dim light.

The guest bathroom door clicks open. Camie steps out, her face scrubbed pink, her blouse buttoned wrong. She stops dead. Her jaw drops. “What the actual fuck?”

They break apart slowly. Izuku keeps his forehead against Katsuki’s, his green eyes sliding toward Camie. They’re calm. Empty. “Is there a problem, sweetheart?”

“A problem?” Camie’s voice pitches high, hysterical. “You’re… he’s… you were just fucking tongue-kissing your mom! That’s fucking sick!”

Katsuki turns his head, just his head, to look at her. The movement is slow, predatory. His arm stays locked around Izuku’s waist. “What did you just say?”

“You heard me! That’s disgusting! I’m calling the cops, I’m—”

“You’re leaving,” Katsuki says. His voice is quiet. It’s the quiet that comes before the explosion. He releases Izuku, but only to take a single step toward her. “You’re gonna walk out that door, and you’re never gonna speak about what you think you saw here. You understand me?”

Camie laughs, a brittle, scared sound. “Or what? You gonna make me? Your freak mommy gonna help?”

Izuku lets out a light, airy sigh. He steps around Katsuki, placing himself slightly between his son and the girl. His bare feet are silent on the marble. “Kacchan, baby, it’s okay. She’s just frightened. She doesn’t understand our family.” He looks at Camie, his head tilted. “We’re very close. A mother’s love can be… intense. It confuses people.”

“Intense? That wasn’t love, that was—”

“It was a kiss goodnight,” Izuku interrupts, his melodic voice cutting through hers without raising a decibel. “My boy had a stressful evening. I was comforting him. You of all people should understand he needs comfort after… exerting himself.” His gaze flicks down to her hastily buttoned blouse, then back to her face. It’s a dismissal. A verdict. “You should go now. Before you say something else you’ll regret.”

Camie’s bravado cracks. She looks from Izuku’s placid, eerie face to Katsuki’s murderous stillness. The foyer feels smaller, the walls closing in. The opulent house isn’t welcoming; it’s a cage. She takes a stumbling step back toward the front door. “You’re both insane,” she whispers.

“The door’s behind you,” Katsuki grunts, not moving. “Use it.”

She fumbles with the heavy lock, her hands shaking. The door swings open, letting in a rush of cold night air. She flees into it without a backward glance. The door clicks shut, leaving a profound silence in its wake.

Katsuki’s shoulders slump, just a fraction. The performance drops. He runs a hand through his spiky hair, exhaling hard. “Fucking idiot.”

Izuku is already moving back to him. His slender fingers reach up, tracing the tense line of Katsuki’s jaw. “My brave boy. Protecting Mommy from the nasty words.” He leans in, his lips brushing the shell of Katsuki’s ear. His whisper is a hot, intimate secret in the quiet house. “You tasted like her, you know. That cheap perfume. I didn’t like it.”

"Let me clean her taste off you," Izuku whispers, leaning in to kiss Katsuki's mouth. It's not a request. His tongue sweeps in, a deliberate, claiming stroke, and he makes a soft, considering sound against Katsuki's lips. "There," he murmurs, pulling back just enough to speak, their breath mingling. "That’s better."

Katsuki's hands find Izuku's hips, his grip hard enough to bruise. "Mommy," he rasps, the word a rough exhale, a surrender and an accusation all at once. He doesn't move to kiss back, just lets Izuku have his mouth, his eyes dark and fixed on his mother's face.

Izuku deepens the kiss, his tongue pushing past Katsuki's lips to sweep the taste of himself back into his son's mouth. It's wet, possessive, and when he finally pulls away, a thread of saliva connects them for a second in the dim light. "There," he breathes, his thumb stroking Katsuki's cheekbone. "All my boy now. Go to bed, Kacchan."

Katsuki's hands stay locked on Izuku's hips, his breathing ragged. He stares down at his mother's flushed face, his own expression unreadable. "Night, Mom," he rasps, the words rough. He doesn't move until Izuku takes a step back, breaking the contact. The space between them feels charged, like the air after a lightning strike.