Biceps | Kim Mingyu
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pairing: boyfriend!mingyu x f!reader genre: jealousy, smut, established relationship synopsis: a harmless touch turns into something mingyu can’t quite shake. he doesn’t rlly say much in the moment. he doesn’t need to. later in the quiet he reminds y/n exactly who she belongs to. rating: 18+(minors do not interact!!!) warnings: jealous sex, jealous!mingyu, dom!mingyu, hmm lowkey mean!mingyu, jealous talk, dirty talk kinda, reader has multiple orgasms, reader teases mingyu?, different positions, overstimulation, edging, cum swallowing, throat fucking, aftercare authors yap note: chat i genuinely liked this story i thought it was so fun to write idek why i swr jealous mingyu is lowkey so fine hello mingyu n scoups biceps have js been speaking to me so i js thought why not write smth mingyu’s a bit harsh but ofc i had to add sprinkles of niceness for realism heh anyways as always hope yall enjoy <3
MASTERLIST
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The restaurant was one of those hidden spots that felt like it had been waiting for them specifically. Dim golden lights bounced off the dark wood, soft jazz hummed from a corner speaker, and the scent of sizzling meat mixed with garlic floated through the air. Mingyu had insisted she come, dragging y/n along like it was non-negotiable, muttering something about “best dumplings outside Seoul” and rolling his eyes when she complained. God forbid she didn’t want to spend her evening with 13 men for once.
When it came time to order drinks, Mingyu split off almost immediately, moving ahead with practiced ease to talk to the staff like he’d been there before. Y/N slowed without thinking, falling into step beside S.Coups as their conversation picked up, casual and easy. They split off unplanned, no one announcing where they were headed because they all already knew.
Seungcheol and Y/N had gotten stuck on gym talk again. It always happened. Complaints about his schedules, jokes about how Seventeen somehow lived between the practice room and the gym room, light teasing about who skipped leg day last.
“You and Mingyu are actually kind of similar,” Y/N said,“You both take the gym seriously.”
He laughed, the sound deep and automatic. He flexed without even realizing he’d done it. Habit. Muscle memory more than ego.
She tilted her head, squinting as if she was inspecting something. Her mouth tugged into a grin.
“Your biceps are kind of the same too.”
And then, without pause, she reached out.
Her fingers wrapped around his arm, squeezing experimentally. Not dramatic. Curious. Amused. Four seconds before she let go, like she’d gathered the information she needed and casually moved on.
It was completely innocent. Maybe even sibling-coded. The kind of thing Y/N did without thinking twice.
“I guess gym finally paid off, right” he laughed. The air stayed light, uncharged, unimportant.
Until Mingyu turned around.
He didn’t even hear the conversation. Didn’t catch the tone or the context. From his angle, all he saw was his girlfriends hand on his best friends arm. The laughter. The comfort.
There was a pause.
Not long enough for anyone else to notice but just long enough for something to tighten in his chest.
“…Oh.”
It showed first in his face. A subtle shift as his brows drew together just slightly as his brain caught up to what his eyes were seeing. He trusted her. He trusted his members. That wasn’t in question.
But instinct didn’t care about logic.
By the time he walked back over, the moment had already passed. His expression smoothed out, features resetting into something neutral and familiar. If someone was watching closely, they might have caught it. That half-second where he chose calm.
“What are you two laughing about?” he asked, voice easy, almost too lazy.
Seungcheol answered, “She was comparing our arms. Said we’re similar.”
Y/N turned to Mingyu and grinned, completely at ease.
“Yeah. Gym bros.”
That did it, as there was no hesitation in her voice, not watching his reaction, wasn’t backtracking or explaining herself. To her, it hadn’t even registered as something that could be weird.
Mingyu let out a breath he hadn’t realized he’d been holding.
He scoffed, rolling his eyes. “Please. Mine are bigger.”
As he spoke, he stepped closer without thinking, his shoulder brushing hers settling his hand lightly at her lower back. Not tight. Not showy. Just there. A quiet, unconscious claim that didn’t need words.
Y/N leaned into him immediately. No glance down. No hesitation. Muscle memory clearly taking over.
Seungcheol noticed, of course. He wasn’t blind. A knowing smirk crossed his face, but he didn’t tease. He just laughed and waved them forward saying, “Alright, alright. Drinks.”
The moment passed. Or at least, it looked like it did.
Later, much later, when the night had quieted and the world had shrunk down to the two of them, it came back up. Mingyu lay on his back beside her, staring at the ceiling like he was thinking about nothing at all. Then, casually, almost lazily, he said, “You’re very handsy, you know that?”
Y/N laughed, confused, turning onto her side. “With who?”
He glanced at her, eyes cutting sideways. “Don’t squeeze my leader’s arm again.”
She blinked. Then laughed harder. “Really?”
“Yeah,” he said, tone calm but firm in that way that meant he was serious even if he didn’t sound it.
She propped herself up on one elbow, eyes bright now. “What happens if I do? Hm? Mingyu?” Her tone was light, playful, but laced with heat that made his pulse quicken.
Pure taunt. Pure tease.
He’d been holding back the whole night but her words ignited him. Mingyu surged up, capturing her mouth in a deep kiss, his hands sliding to her waist to haul her against him. She melted into it, fingers threading through his hair as their tongues tangled. He broke away, breath ragged, and stripped her shirt over her head, tossing it aside. Her bra followed, freeing her breasts, nipples already hardening in the cool air. “You want to know what I'll do?' he growled, shoving her back onto the couch and climbing over her. 'I'll fuck you until you forget anyone else's name.”
Y/N’s hands gripped his biceps, nails digging in as he yanked her pants down her legs, leaving her bare. He shed his own clothes quickly, his cock springing free, thick and hard. Positioning himself between her thighs in missionary, he rubbed the head along her slick pussy, coating himself in her wetness. “Spread for me,” he ordered, and she did, legs falling open wider. He pushed in slowly, inch by inch, stretching her walls until he was buried to the max.
“Fuck, so tight,” he grunted, holding still to let her adjust. Y/N’s grip tightened on his arms, her body arching up. He started thrusting, deep and steady, each slide pulling moans from her throat. “Seungcheol can't fuck you like this, can he?” Mingyu demanded, voice harsh as he picked up pace, hips snapping forward. “Can he? Answer me.”
Y/N could only whimper, her head tossing side to side, words lost in the building pleasure. “M-Mingyu...” she gasped, but he slowed, pulling almost all the way out, denying her the friction. “Answer,” he repeated, circling her clit with his thumb but not enough to push her over. She bucked her hips desperately, holding onto his thick biceps like a lifeline, muscles straining under her fingers. “No... only you...”
Satisfied, he slammed back in, fucking her harder, his free hand pinning her hip down. He edged her twice more, bringing her to the brink with relentless strokes and clit rubs, then stopping, making her sob with need. “Beg for it,” he said, teeth grazing her neck. “Please, Mingyu, let me cum,” she pleaded, voice breaking. He drove into her faster, thumb pressing her clit until she shattered, pussy clenching around him in waves, but he pulled out before he could finish, chest heaving.
“On your knees,” he commanded, sitting back. Y/N scrambled up, mouth watering at the sight of his slick cock. She took him in, lips wrapping around the head, tongue swirling as she bobbed down, taking him deep. Her hands braced on his thighs, but he grabbed her hair, guiding her rhythm. “Suck it like you mean it,” he said roughly, thrusting shallowly into her mouth. She hollowed her cheeks, gagging slightly as he hit the back of her throat, saliva dripping down her chin. The sight pushed him over—“Fuck, take it”—and he came, hot spurts filling her mouth. Y/N swallowed greedily, licking him clean with a dazed smile.
Not done, Mingyu flipped her onto all fours, gripping her hips and slamming back inside her soaked pussy. “Still dripping for me,” he said, spanking her ass lightly. He fucked her brutally, balls slapping her ass, one hand reaching around to pinch her nipple. Y/N pushed back, moaning loudly, but he didn't let up, overstimulating her sensitive nerves. Her second orgasm hit fast and hard from the relentless pace, body shaking as she cried out, but he kept thrusting through it, drawing out whimpers that bordered on pain and pleasure.
“Can't stop now,” he growled, pulling out to stroke himself. He came on her back in thick ropes, marking her skin, watching it pool on her. Y/N collapsed forward, panting, but he wasn't finished. He rolled her onto her back again, sliding into her cum-slick pussy for the final round in missionary. “One more, I know you can do one more baby,”he murmured, slower now but deep, her legs wrapping around him. She clutched his biceps again, pulling him closer as he ground against her g-spot.
“You're mine,” he said, jealousy flaring in his tone. “Seungcheol can't have this—can't make you scream like I do.” Y/N nodded frantically, another orgasm building from the overstimulation, her moans incoherent. He chased his own release, thrusting erratically until he buried deep and came inside her, flooding her with warmth, mixing with her juices.
They both slumped, sweaty and spent. Mingyu pulled out gently, kissing her, grabbing a warm cloth from the bathroom to clean her up, wiping her stomach and between her legs with care. He tucked her into his side under the blankets, pressing soft kisses to her temple. “You okay?” he asked, voice tender now.
Y/N nuzzled his chest, tracing his arm. “Yeah... and I won't touch his arm again. Promise.” She smiled up at him, and he chuckled, holding her tighter, enveloping her in his warmth.
