The cold, polished marble of the main altar seared a line of fire across Izuku’s bare back. Katsuki’s weight pinned him against the sacred table, their earlier spend a slick, cooling sacrament beneath his thighs. Each brutal thrust drove his shoulder blades into the carved edge of the crucifix inlaid on the altar’s front, a pain so sharp it felt like consecration.

“Look at them,” Katsuki snarled, his voice raw. He fisted a hand in Izuku’s green curls and wrenched his head to the side. The stained-glass saints watched, their colored light painting Katsuki’s face in hues of hellfire and grace. “They see you. They see what you are.”

Izuku could hardly hold back anymore. A broken, ragged sound tore from his throat and he bucked his hips back, meeting every drive of the priest’s cock. The loud, wet slap of Katsuki’s balls against his ass echoed off the stone vaults.

“More,” Izuku gasped, the word mangled. “Please, Father—more—”

“Begging for it on God’s own table.” Katsuki’s hips pistoned, his breath hot against Izuku’s ear. “You filthy little thing. You love this. Say it.”

“I love it,” Izuku sobbed, his nails scratching against the marble. His small, binderless chest was bouncing at each thrust, his nipples hard and aching. “I love your cock, I love it—”

Katsuki’s hand slid from his hair down to his throat, not squeezing, just holding. A claim. “Whose are you?”

“Yours.” The answer was immediate, wrenched from some deep, corrupted place inside him. “I’m yours.”

The rhythm turned punishing, each thrust punching the air from Izuku’s lungs. The pain in his shoulders bloomed bright and hot, a counterpoint to the devastating fullness below. He was dripping, wrecked, the sounds obscene.

Katsuki’s other hand smoothed over the freckled skin of Izuku’s hip, a grotesque parody of tenderness. “This is your true baptism. Not water.” He drove home, deep. “Filth. This is your sacrament.”

Izuku’s vision swam with colored light from the windows. He was crying again, tears smearing the polished black marble. His body was a live wire, every nerve screaming for the finish only Katsuki could give him. He pushed back, desperate, taking every inch. “Don’t stop. Please, don’t ever stop.”

Katsuki’s laugh was a dark, breathless thing. His hips stuttered, his control fraying. “Then take it. Take all of it.”

The reckless, deep rhythm didn’t stop. It stole the air from Izuku’s lungs, carved a fire in his core, built a pressure so immense he couldn’t think. Katsuki’s cock hit a place inside him that made his vision whiten, over and over, a brutal piston stoking a wildfire. He felt his own climax rip through him without a single touch to his clit—a shocking, violent unraveling. A strangled scream tore from his throat as he came, his body seizing. His pussy clenched and fluttered around Katsuki’s length, and he squirted, a hot fountain of release that splattered across the cold marble altar and pooled on the floor beneath them with a sound like rain.

The force of it left him trembling, boneless, but Katsuki didn’t slow. He fucked him through the convulsions, his grip on Izuku’s hip bruising. “Look at the mess you made,” he growled, his thrusts turning jagged. “On God’s table. You ruined it.”

Izuku could only gasp, oversensitive and shattered. His head rested against the marble, smearing tears and sweat. In the heaving silence that followed his own release, the need for Katsuki’s became a physical ache. “Father,” he begged, his voice a wrecked whisper. “Please. Your… your cum. I need it. Fill me up.”

“Needy thing.” Katsuki’s breath hitched. His rhythm faltered, his own control snapping. “You want it that badly?”

“Yes,” Izuku sobbed, pushing back weakly against him. “Mark me. Please. I want it inside. I want to feel it.”

That was all it took. Katsuki drove in one last, brutal time and went rigid. A raw, guttural sound was punched from his chest as he came, his hips stuttering against Izuku’s ass. Izuku felt the hot flood deep inside, pulse after pulse, a claiming so intimate it made him whimper. Katsuki slumped over him, his weight a heavy, sweating blanket, his forehead pressed between Izuku’s chest.

For a long moment, there was only the sound of their ragged breathing and the distant drip of water from a candle sconce. The colored light from the saints shifted as a cloud passed outside.

Katsuki shifted first. He pulled out slowly, and Izuku cried out at the sudden emptiness, at the wet, leaking feeling that followed. Katsuki’s hands, surprisingly gentle on him. Izuku winced as the cold marble kissed his abused skin.

Katsuki looked down at him, his crimson eyes scanning the mess: the tears, the spend, the freckled chest heaving. He reached out and thumbed away a tear tracking through Izuku’s temple. The gesture was at odds with everything. “See?” Katsuki’s voice was low, almost hoarse. “This is what you are. My altar. My sacrament.”

Izuku stared up at him, his green eyes wide and hollow. He didn’t argue. He just lifted a trembling hand and touched Katsuki’s wrist where it rested near his face. A silent acknowledgment. A surrender so complete it felt like peace.

Izuku’s trembling hand slid from Katsuki’s wrist to the back of his neck. He pulled, with a surprising, quiet strength, drawing the priest’s mouth down to his own. Katsuki went still, his crimson eyes widening a fraction before they closed. He didn’t resist. He kissed him back.

It wasn’t like before—not a biting, claiming thing. It was deep, slow, and shockingly passionate. Katsuki’s lips moved against his, tasting of salt and sin, his tongue sweeping into Izuku’s mouth with a possessive gentleness that stole the air from his lungs. His big hands came up to cradle Izuku’s face, thumbs stroking the tear tracks on his freckled cheeks.

When they broke apart, both were breathless. Izuku’s green eyes searched Katsuki’s face, wide with a stunned wonder. “Father…”

“Shut up,” Katsuki murmured, but there was no heat in it. He leaned his forehead against Izuku’s, his own eyes shut tight. He was holding Izuku’s wet, spent body flush against his own, skin to skin, his own softening cock still nestled in the mess between Izuku’s thighs. “Just… be quiet.”

“Why are you doing that?” Izuku whispered, his voice cracked. “The kiss… why did you kiss me like that?”

Katsuki’s jaw tightened. He opened his eyes, and the hellfire red had dimmed to a smoldering ember. “I don’t know.” The admission was raw, ripped from him. He looked as unsettled as Izuku felt. “I just… wanted to.”

He shifted, pulling Izuku up and against his chest, turning them so Izuku’s back was to the cold altar, held in the circle of his arms. Izuku went, pliant, his small frame shaking. He buried his face in the curve of Katsuki’s neck, breathing in the scent of sweat, incense, and them.

“I am yours, Father…” Izuku whispered against the skin of Katsuki’s neck, the words muffled but clear.

Katsuki went utterly still. The arms holding Izuku against his chest tightened, a reflexive, almost painful squeeze. He pulled back just enough to look down at him, his crimson eyes searching Izuku’s face. “What did you say?”

“I’m yours.” Izuku’s green eyes were glazed, wrecked, but utterly earnest. He said it again, stronger. “You asked. Before. And it’s true. I’m yours.”

A low, ragged sound vibrated in Katsuki’s chest. It wasn’t a laugh. It was something pained. “You don’t know what you’re saying.”

Katsuki claimed his mouth again, this time with a raw, possessive hunger that stole the air from Izuku’s lungs. His tongue plunged deep, tasting the salt of sweat and the faint copper of blood from a bitten lip. It was a kiss that felt like a brand.

Katsuki broke the kiss, his lips hovering a breath from Izuku's. His crimson eyes burned in the dim, colored light. "Next time," he whispered, the words a dark vibration against Izuku's mouth, "I'm going to fuck you in the sacristy. Right where I first saw you. Where you thought you were safe."

Izuku shuddered, a fresh tremor running through his oversensitive body. He was still leaking Katsuki’s release onto the cold altar. "Father…"

"I'm going to bend you over the vestment case," Katsuki continued, his voice a low, thrilling rasp. His hand slid down Izuku's spine, possessive. "You'll look at your own reflection in the polished wood while I take you from behind. You'll watch your face when you come."

"Why?" Izuku breathed, his green eyes wide, fixed on Katsuki's. He wasn't refusing. He was begging for the reason.

"Because I want to see it," Katsuki said, his thumb tracing the line of Izuku's jaw. "I want to see the exact moment my cock ruins you. Every time. I want to own that, too."

He shifted his weight, pulling Izuku more firmly against him. The movement made Izuku gasp—a sharp, wet sound in the quiet. Katsuki’s own spend was a slick warmth between Izuku’s thighs, a claimed, filthy truth.

"And after," Katsuki murmured, his lips brushing Izuku's ear, "I'm going to make you kneel on the sacristy floor. You're going to open your mouth, and you're going to clean me with your tongue. Every drop. You're going to swallow what I put in you, and you're going to thank God for the privilege."

Izuku’s breath hitched. A weak, broken sound of want escaped him. His head fell back against Katsuki’s shoulder, exposing his throat. "Yes."

"You're eager for it," Katsuki observed, his tone shifting to something colder, more analytical. He pressed two fingers against Izuku’s lower stomach, where he was full and leaking. Izuku cried out, his body clenching weakly around nothing. "Look at you. Soaked in me. Ruined for anything else."

"You ruined me," Izuku agreed, the words a wrecked confession. He turned his face into Katsuki's neck, hiding. "You did."

Katsuki held him there, in the silence of the defiled sanctuary. His hands, broad and hot, smoothed over the freckled skin of Izuku's arms, a gesture that could almost be comfort if not for the words still hanging in the air like incense. "Good," he finally said, the single word final. A blessing and a curse.