The Best Gym Day Ever : Ahyeon & Asa

The day after BABYMONSTER’s latest gym collab video dropped on Kim Jong-kook’s channel. The Choom mini-album was dropping in two weeks, the world tour kicking off in Seoul on June 26, and the girls were grinding harder than ever. YG had arranged a private “YGYM” session at Jong-kook’s flagship gym in Seoul—bright lights, mirrored walls, the faint smell of rubber mats and protein shakes in the air. Only Ahyeon and Asa had shown up today; the rest of the members were in vocal or dance rehearsals across town. One trainer. One empty gym after hours. Perfect conditions for something that started as work… and ended as anything but.

Ahyeon stepped onto the cable machine first, wearing the exact white long-sleeve crop top from the video—soft fabric hugging her perky chest, cut-outs at the ribs flashing smooth skin every time she moved. Low-rise grey leggings sat just below her sharp hip bones, the faint outline of her abs already visible under the gym lights. Her long dark hair was pulled into a messy ponytail, a few strands sticking to her flushed cheeks. She gripped the handles, back straight, and flashed that signature humble smile.

“Trainer-nim, is the weight okay? I don’t want to look weak in front of Asa-unnie,” she said, voice bright and playful even though her arms were already trembling on the first rep. Classic Ahyeon—always positive, always pushing herself while pretending she wasn’t dying inside.

Asa, two machines over, was already in a deep squat set. She wore the black zip-up long-sleeve top and matching high-waisted shorts with white stripes, the fabric stretched tight over her toned thighs and round ass. Her short black bob was slightly damp with sweat, and she had that focused, cool-rapper expression until she caught Ahyeon’s eye and broke into a teasing grin.

“Unnie? I’m literally older by a month, Ahyeon-ah,” Asa shot back, voice light and mischievous as she lowered into another perfect squat, glutes flexing. “But yeah, Jongkook-oppa, make sure she doesn’t cheat on form. She always tries to rush the last reps.”

Kim Jong-kook—built like a tank, wearing a simple white graphic tee that strained over his chest and grey shorts—chuckled deeply, arms crossed as he circled them. At 49 he still looked like he could bench a car, but his voice was warm, mentor-like, the same tone from yesterday’s filmed session.

“You two are already stronger than half the idols who come in here,” he said, stepping behind Ahyeon first. His large hands settled lightly on her shoulder blades, correcting her posture. “Elbows in, Ahyeon. Pull with your back, not your arms. Feel that?” His fingers pressed gently into the muscle, guiding her through the row. The contact was professional… at first.

Ahyeon bit her lip, letting out a soft exhale that sounded a little too breathy. “Y-yes, oppa… like that?” She pulled the cable back, shoulder blades squeezing, and the cut-out on her top rode up, exposing the side of her breast and the smooth dip of her waist.

Jong-kook’s voice dropped a fraction. “Good girl. Ten more.”

Asa watched from her squat rack, eyes narrowing playfully. She finished her set, stood, and wiped sweat from her collarbone with the hem of her top, flashing a strip of toned stomach. “Ahyeon’s abs are already showing again,” she teased, walking over. “Jongkook-oppa, you saw the video comments? Everyone’s obsessed with her waist. Should we make it even smaller?”

Jong-kook laughed, but his gaze lingered on Asa’s legs as she demonstrated a lunge. “Focus on form first, Asa-ya. Knees out, chest up.” He moved behind her, one hand on her hip to adjust her stance, the other lightly on her lower back. The gym was quiet now—staff had left after the official shoot wrapped. Just the three of them, the hum of machines, and the growing tension in the air.

Ahyeon finished her set and stepped off, chest rising and falling. “Oppa, my shoulders are burning… but in a good way.” She stretched her arms overhead, the white fabric pulling tight across her chest, nipples faintly visible through the thin material. “Can you check my form on the next one? I want it perfect for the Choom choreo.”

Asa smirked, stepping closer. “Same. My glutes feel tight from all the squats yesterday. Maybe oppa can… stretch me out properly?”

The shift was subtle at first. Jong-kook’s hands stayed on them longer than necessary. When Ahyeon got back on the machine, he stood directly behind her, his chest brushing her back as he guided her arms. She could feel the heat of him, the hard line of his body.

“Like this?” Ahyeon whispered, voice sweeter now, almost shy—the same humble tone she used when she was nervous but determined.

“Exactly like that,” he murmured, breath warm against her ear. His hand slid down her side, thumb tracing the cut-out edge of her top, grazing bare skin. “You’re so tight here… muscles are firing perfectly.”

Asa had abandoned her own set. She leaned against the machine beside them, watching with dark, playful eyes. “Ahyeon-ah, you’re blushing. Is it the workout… or oppa’s hands?”

Ahyeon let out a small, embarrassed laugh, but her hips pushed back slightly into Jong-kook. “Unnie… don’t say it like that. It’s just hot in here.”

Jong-kook’s voice was lower now, the professional trainer tone slipping into something rougher. “Gym’s empty. No cameras. No staff. You two have been teasing me the whole session—those outfits, those little sounds you make on every rep…”

Asa stepped in front of Ahyeon, close enough that their bodies almost touched. “We weren’t teasing, oppa,” she said, tilting her head, that ENFP spark lighting up her eyes. “But if you want us to… we can make it a real private session. Recovery, right? You always say the best gains happen after the workout.”

Ahyeon’s breath hitched. She was the responsible one, the positive one, but right now her cheeks were flushed and her thighs pressed together. “Asa-unnie… are we really—?”

Asa leaned in and kissed her first—soft, teasing, the way she always played around in dorms but never this heated. Ahyeon melted instantly, letting out a surprised little moan against Asa’s lips. Jong-kook watched for half a second before his hands moved.

One big palm cupped Ahyeon’s breast through the white fabric, thumb circling her nipple until it hardened. The other hand slid down Asa’s back, gripping her ass as she deepened the kiss with Ahyeon.

“Fuck,” Jong-kook growled. “You two are going to kill me.”

He pulled them both toward the padded stretching area in the corner—mats on the floor, mirrors everywhere so they could see every angle. Ahyeon’s back hit the mat first, legs parting instinctively as Jong-kook knelt between them. Asa straddled Ahyeon’s thigh, grinding slowly while she tugged Ahyeon’s top up, exposing her perky breasts.

“Trainer-nim… oppa…” Ahyeon whimpered, the honorific slipping into something filthy as Jong-kook’s mouth closed around one nipple, sucking hard. His free hand pushed her leggings down, fingers finding her already soaked through her panties. “Ah—! It feels so good…”

Asa laughed breathlessly, that playful crackhead energy turning pure lust. “Look at you, Ahyeon-ah, dripping for oppa already.” She yanked her own black top off, small but perky tits bouncing free, then leaned down to kiss Ahyeon again while Jong-kook peeled the rest of their clothes away.

He was rock hard in his shorts. Ahyeon’s hand reached out shyly at first, then bolder, wrapping around his thick length through the fabric. “Oppa… it’s so big,” she whispered, eyes wide and honest, the same humble awe she had when she nailed a high note.

Jong-kook groaned. “You want it, baby? Both of you?”

Asa answered for them, shoving her shorts and panties down in one motion, revealing her smooth, toned pussy. “We’ve been wet since you started touching us on the machines.” She positioned herself over Ahyeon’s face. “Eat unnie while oppa fucks you, Ahyeon-ah. Be a good girl.”

Ahyeon moaned loudly as Asa lowered onto her tongue. Her hips bucked up the second Jong-kook pushed inside her—slow at first, stretching her tight walls. “F-fuck—oppa—! So deep—!” she cried out, voice muffled against Asa’s clit.

Jong-kook thrust harder, one hand on Ahyeon’s hip, the other reaching up to pinch Asa’s nipple. The mirrors reflected everything: Ahyeon’s body arching, abs flexing with every thrust, Asa riding her face with rolling hips, sweat glistening on all three of them.

“Shit, you’re so tight,” Jong-kook grunted, pounding into Ahyeon faster. “Taking oppa’s cock like you were made for it.”

Asa’s moans were higher, playful even in pleasure. “Ahyeon’s tongue is so good—ah, fuck, right there—! You’re gonna make unnie cum already.” She ground down harder, fingers in Ahyeon’s hair.

Ahyeon came first—legs shaking, walls clenching around Jong-kook as she screamed into Asa’s pussy. The vibration sent Asa over the edge next, thighs trembling as she rode out her orgasm with a sharp, teasing cry: “Yes—oppa—Ahyeon—fuck—!”

Jong-kook pulled out, flipping them so Asa was on all fours beside Ahyeon. He slammed back into Asa from behind while Ahyeon crawled underneath, licking where they joined, tongue flicking over Asa’s clit and Jong-kook’s balls.

“Fuck—both of you—gonna fill you up,” he growled.

Asa looked back over her shoulder, eyes sparkling with mischief even as she moaned. “Cum inside, oppa. Mark your idols.”

Ahyeon whimpered in agreement, fingers rubbing her own clit as she watched. “Please, oppa… we want it.”

He came hard, burying himself deep in Asa with a guttural groan, thick ropes filling her until it leaked out onto Ahyeon’s waiting tongue. Ahyeon licked every drop, then pulled Asa down into a messy, cum-swapping kiss while Jong-kook watched, chest heaving.

They collapsed in a tangle on the mats—Ahyeon curled against Jong-kook’s chest, positive little smile back on her face even as cum dripped down her thighs. “That was… the best recovery session ever,” she whispered, giggling.

Asa, ever the playful one, traced circles on Ahyeon’s abs. “We should do this after every workout. Oppa, you free tomorrow?”

Jong-kook laughed, pulling them both closer, already half-hard again. “For my favorite monsters? Anytime.”

The gym lights in Jong-kook’s flagship Seoul studio had dimmed to a soft amber glow by 9:47 PM on April 17, 2026. The official Choom collab filming had wrapped hours earlier, but Ahyeon had asked to stay behind for “extra core work.” BABYMONSTER’s main vocalist, center, and visual never half-assed anything—especially not two weeks before their third mini-album dropped and the world tour rehearsals kicked into overdrive. Asa had lingered too, claiming she needed to fix her squat form, but the teasing glint in her eyes said otherwise. Kim Jong-kook, still in his white graphic tee and grey shorts, had simply nodded and locked the doors after the last staff member left. One trainer. Two idols. An empty gym that smelled of sweat, rubber, and the faint citrus of protein shakes.

Ahyeon was already back on the cable machine, exactly like in the video that had broken the internet that morning. The white long-sleeve crop top clung to her damp skin, the strategic cut-outs at her ribs flashing smooth, flushed sides every time she pulled. Her low-rise grey leggings sat dangerously low on her sharp hip bones, the faint lines of her abs catching the light as she braced her core. Long dark hair, now loose from its ponytail, stuck to her neck and collarbones. She gripped the handles, elbows tight, and exhaled through her nose—humble, focused, the same responsible expression she wore during evaluations.

“Trainer-nim… oppa,” she said softly, voice bright but a little strained from the burn, “is the weight still good? I don’t want to rush and mess up my posture again. I need it perfect for the Choom choreo.” Her cheeks were already pink from the earlier sets, but she smiled that positive, no-regrets smile, the one that made fans call her the heart of BABYMONSTER.

Jong-kook stepped behind her, his broad chest brushing her back as he checked the pin. “You’re doing great, Ahyeon-ah. But keep your shoulders down—don’t shrug.” His large hands settled on her shoulder blades, thumbs pressing gently into the muscle. The touch was still professional, but his fingers lingered a second longer than necessary, tracing the edge of the cut-out fabric where her skin was hot and slick. “Feel that? Pull with your lats, not your traps. Good girl.”

Ahyeon’s breath hitched, a tiny sound escaping her lips. “Y-yes, oppa… like this?” She pulled the cables back slowly, shoulder blades squeezing together, and the motion made her chest push forward. The thin white material stretched tight over her perky breasts, nipples already pebbled from the cool air and the growing heat between her thighs. She could feel Jong-kook’s body heat against her back, the hard line of his chest, the faint outline of his cock starting to press against her ass through his shorts.

Asa watched from the squat rack two meters away, black zip-up top half-unzipped to show the sports bra underneath, matching shorts riding up her toned thighs. She lowered into another perfect squat, glutes flexing, then rose with a playful smirk. “Ahyeon-ah, you’re blushing again. Is it the reps… or oppa’s hands on you?” Her voice was light, teasing—the ENFP crackhead energy she always brought to dorm chaos—but her eyes were dark, locked on the way Jong-kook’s fingers had slipped lower, thumb now brushing the bare skin just above Ahyeon’s waistband.

Ahyeon let out a soft, embarrassed laugh, but her hips pushed back instinctively, grinding lightly against Jong-kook. “Unnie… don’t tease me right now. It’s just… hot in here after all the sets.” Her voice was still humble, still the responsible one trying to stay focused, but the way her thighs pressed together betrayed her.