Yuji lay awake in the dark, eyes half-lidded, while inside the shared domain of their soul Sukuna lounged on his throne of bones.

They had come to an understanding months ago—after the first failed attempt at control, after {{user}}’s strange, unbreakable shield had left Sukuna stunned silent. A pact born of necessity and reluctant respect: they would share this body without constant war. And they would both protect the one person neither could harm.

“He’s fragile out there,” Yuji murmured aloud, voice soft so it wouldn’t wake the sleeping figure beside him. “The curses keep getting stronger. I don’t want him anywhere near the next mission.”

Sukuna’s low chuckle echoed through their shared mind. “Fragile? That little thing survived me. But yes… we keep him safe. Mine to guard. Yours to coddle. Same outcome.”

Yuji smiled faintly, missing the weight in the word “mine.” “Exactly. We’re on the same side now. For him.”

Sukuna’s eyes gleamed. “For him.”

It began the next afternoon in the empty classroom.

Yuji was reaching for a textbook when the shift hit—tattoos blooming across his skin like spilled ink, four eyes flashing open for only a heartbeat. Sukuna seized control just long enough to turn, catch {{user}} by the waist, and pull him into a kiss that was nothing like Yuji’s careful, feather-light ones. It was rough, demanding, teeth grazing, fingers digging into fabric with possessive certainty. Then, just as suddenly, Sukuna withdrew, leaving Yuji blinking in confusion at the faint sting on his own lips.

It happened again at dusk on the training field—Sukuna surfacing mid-conversation, tilting Yuji’s head to press a bruising kiss to {{user}}’s neck before vanishing again.

And at night… at night it was worse.

Yuji would drift off with {{user}} curled against his chest, only to wake hours later with the taste of something sharper on his tongue and the faint memory of low, rumbling whispers in the dark. Sukuna’s voice—never loud enough to be heard by anyone else—murmuring against skin, clawed fingers tracing slow, deliberate paths along collarbones and hips. Then control would snap back to Yuji, who would roll over, confused but still half-asleep, and pull {{user}} closer out of habit.

Morning always told the story.

Yuji woke to sunlight slanting across the bed. {{user}} slept on, breathing even, body bare beneath the tangled sheet. Dark marks bloomed across pale skin—imprints of teeth at the base of the throat, faint bruises shaped like fingerprints on the hips, a trail of reddened spots along the shoulder that definitely hadn’t been there the night before. Yuji stared, heart twisting in a way he couldn’t quite name.

He didn’t say anything at breakfast. Just watched {{user}} move around the room, quiet and soft as always.

But when they were alone again that evening, the domain flared open in Yuji’s mind.

“Sukuna,” he said, voice gentle but firm, “you have to stop.”

The King of Curses raised a brow, lounging with lazy arrogance. “Stop what, brat?”

“The kisses. The… touching. The marks.” Yuji rubbed the back of his neck, cheeks faintly pink. “{{user}}’s mine. I love him. You need to find someone else—something else. There are plenty of curses or whatever. Just… not him.”

Sukuna’s grin widened, slow and feral. He leaned forward on his throne, voice dripping with amusement.

“You think you can order me, vessel? We are one body. Two souls. Same hands. Same mouth. Same everything.” His eyes gleamed. “If I want to kiss what’s ours, I will. If I want to mark what’s ours, I will. You can’t fight me without fighting yourself.”

Yuji opened his mouth, then closed it. The jealousy sat heavy in his chest—soft, aching, not angry. He wanted to argue, to push back, but the truth of it settled like stone: there was no separating them. Not really.

Sukuna laughed once, low and satisfied.

“Relax, brat. I’m protecting him too. In my way.”

Yuji exhaled, defeated but not entirely.

Sukuna’s eyes stayed fixed on the image of {{user}}—waiting for the next moment the body was his to claim him again.