Mine.
Character: Yeon Si-eun x Reader Setting: High school AU (canon-adjacent) Tone: Dark, jealous, possessive, rough smut Length: ~500 words
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The hallway noise blurred around Si-eun as he stood at the edge of the corridor, eyes locked on Y/N.
She was laughing. Smiling in that soft, unaware way she always did. But it wasn’t him she was smiling at.
Some guy — tall, too confident, standing a little too close — leaned into her space. Said something that made her glance down, hiding a grin behind her hand. The guy chuckled. Tapped her notebook. Said something else that made her tilt her head and laugh again.
Si-eun didn’t move.
His expression didn’t shift. But something dark crawled under his skin, tight and coiled, like a fuse was lit deep in his stomach and no one could see the smoke.
He waited.
Didn’t say a word when she passed him later between classes, offering a small wave.
Didn’t say a word when the guy — that guy — brushed past him in the stairwell.
Didn’t say a word when final period ended, and he was already moving, fast and quiet, to the third floor. The one that always emptied early.
He knew she had forgotten something in the classroom. She always did.
And when he heard the light click of the door, the way she pushed it open and stepped inside alone — he followed.
Soft footsteps. Door sliding closed behind him.
Click.
Locked.
Y/N spun halfway, startled. “Si-eun?”
He didn’t answer.
Didn’t even blink.
She barely got a second to breathe before her back hit the door, a palm splayed beside her head. Si-eun’s body pressed into hers — not fully, not yet — but close enough to feel the heat rolling off him. His breath was sharp. Controlled. Barely.
“Wh—what are you—?”
“You’re mine.” His voice was low. Rough. The words scraped the air like they’d been locked in his throat all day. “You know that, right?”
Y/N blinked. “Wha—?”
His mouth crashed against hers — no warning, no hesitation — and her gasp was swallowed whole. His kiss was rough. Desperate. Tongue pushing in like he needed to replace the taste of anyone who’d ever dared get close.
“You smiled at him.” His mouth moved down to her jaw, then lower, biting at her throat. “Laughed. Touched him.”
“I—he was just—”
Si-eun grabbed her wrist. Lifted it above her head, pinning it hard to the door. “Don’t lie to me.”
His free hand slid under her skirt. Rough fingertips pushing between her thighs, over her underwear, already damp from the heat of him. “You’re wet.”
She whimpered. “Si-eun—”
His grip on her tightened. “You smiled at him like this?”
“No—” she gasped, “I didn’t—”
“You’re mine,” he growled again, voice low and wrecked, like he couldn’t say it enough.
He pushed her panties aside and slid two fingers in, no preamble. Just filthy, possessive urgency. His forehead dropped to hers as he fingered her hard — fast and unforgiving — like he was trying to erase someone else’s gaze from her skin.
“Say it,” he breathed. “Say who you belong to.”
Y/N moaned, body arching, wrist straining under his grip. “You—Si-eun—I’m yours—”
“Louder.”
“I’m yours!”
He bit her shoulder, dragging his teeth over her skin as she cried out. Her body shook, torn between fear and the need he always ripped from her so easily.
He undid his belt one-handed. Pulled himself out, hard and flushed, tip already leaking from how long he’d been clenching his jaw all day, watching her from a distance, fury simmering under the surface.
“Turn around.”
She blinked, dazed.
“Now, Y/N. Hands on the door.”
She obeyed, trembling.
Skirt flipped up. Panties pulled down just enough. She barely had time to breathe before he shoved in, burying himself deep with a choked curse against her shoulder.
“So fucking tight,” he hissed.
He didn’t ease into it. Didn’t give her the gentle rhythm he usually did.
He took.
Thrust after brutal thrust, like he was trying to ruin her. Mark her from the inside. His fingers gripped her hips so tight she knew she’d bruise. And she didn’t care.
Because it was him.
Yeon Si-eun, who never said much. Who never acted out. Who always watched from a distance. Cold. Calm. Calculated.
But now—
Now he was falling apart behind her. Fucking her like something inside him had snapped.
“Tell me,” he groaned. “Tell me you don’t want anyone else.”
“I don’t—I swear—”
“Tell me you’re mine.”
“I’m yours, Si-eun. Only yours—”
He slammed deeper, burying himself to the hilt, grinding in as her body clenched and her moans spilled raw and broken from her throat. Her legs were shaking. Nails digging into the wood of the door.
“I saw him looking at you,” he said, breath shuddering. “I wanted to break his fucking fingers.”
“Don’t—” she panted, “don’t think about him, please—”
“I’m not,” he growled, thrusting again, harder, rougher. “I’m thinking about how you feel around me. How you moan for me. How no one else gets to see this.”
He reached down, rubbing her clit in tight, punishing circles, dragging her closer and closer to the edge. She was falling apart, the sound of skin slapping echoing off the walls, the sharp, guttural noise of his breathing loud in her ears.
She cried out when she came, gasping his name, body pulsing around him so tightly he groaned deep, like he was in pain.
And then he pulled out. Grabbed her hips again. Slammed back in even rougher.
He wasn’t done.
Not even close.
He wasn’t going to stop until the only name she could remember was his.
Until no one else even existed.
