!!!![THESE STORIES ARE ALL FICTIONAL AND HAVE NO RELATIONSHIP TO THE REAL WORLD]!!!!!

!!!!!!!All characters are 18+ no matter if stated otherwise!!!!!!

The sun blazed overhead, turning the backyard into a shimmering oven. It was the kind of Sunday that demanded a dip in the pool, and Kaito had reluctantly agreed to join Mio after she'd whined about it all morning. He figured he could handle an hour or two of her usual nonsense—maybe even relax for once—big mistake.

He was already lounging by the pool, sprawled on a deck chair in his swim trunks, sunglasses perched on his nose, when Mio made her grand entrance. The sliding glass door creaked open, and out she stepped, a vision designed to ruin his day. Her "bikini" was less clothing and more a collection of strings with scraps of fabric attached—bright pink, barely-there triangles that tied around her neck and hips, leaving miles of skin exposed. The top strained against her perky chest, the knots looking one tug away from giving up entirely. The bottoms? A thong so skimpy it was practically a suggestion, hugging her curves and flashing her ass cheeks with every step.

Kaito's sunglasses slipped down his nose as his jaw dropped. "What the hell are you wearing, Mio?!" he sputtered, sitting up so fast he nearly tipped the chair over.

Mio twirled, her twin tails bouncing, and shot him a smug grin. "My new bikini, Onii-chan! Isn't it cute? I picked it out just for today~" She struck a pose, hands on her hips, thrusting her chest out so the tiny triangles shifted dangerously.

"Cute?!" he choked, yanking his sunglasses off to glare at her. "That's not a bikini—it's dental floss! Go put on something normal before Mom sees you!"

"Mom's out shopping all day," Mio chirped, skipping closer to the pool's edge. "It's just you and me, Onii-chan. No one to tattle~" She bent over to adjust her sandal, giving him an eyeful of her barely-covered backside, the thong disappearing between her cheeks. She glanced back, catching him staring, and winked. "Like the view?"

"I'm not looking!" he snapped, though his flushed face told a different story. He crossed his arms, slumping back in the chair like he could will himself into invisibility. "You're such a perv."

"Me? A perv?" Mio gasped, pressing a hand to her chest—accidentally (or not) nudging the bikini top so it slipped just enough to flash a hint of nipple. "I'm just trying to enjoy the pool! You're the one getting all hot and bothered over your innocent little sister."

"Innocent my ass," he muttered, grabbing a towel to drape over his lap—just in case. Inside, his heart was doing cartwheels. She looked ridiculous—ridiculously hot, that is—and he hated how much he didn't hate it. The way the sun glinted off her skin, the way the bikini clung to her like it was painted on… he was in deep trouble.

Mio wasn't about to let him off easy. She sauntered over to the pool's edge, hips swaying, and dipped a toe in the water. "Ooh, it's so nice~" she cooed, then turned to face him. Without warning, she started swaying her hips, rolling them in a slow, deliberate twerk. The thong bikini did nothing to hide the jiggle of her ass cheeks, each bounce a calculated taunt. "How's my dance, Onii-chan? Think I could go viral?"

Kaito's eyes widened, and he choked on his own spit. "S-stop that! What are you even doing? You look like an idiot!"

"An idiot you can't stop staring at~" she teased, twerking faster, the strings of her bikini bouncing with her. She spun around, hands on her knees, and gave him a full-on show, her cheeks practically winking at him. "Come on, admit it—you love watching your naughty little sister shake it."

"I do not!" he yelled, though his voice cracked like a teenager's. He grabbed a soda can from the cooler and pressed it to his forehead, desperate to cool off. "You're gonna give me a heart attack, you lunatic."

Mio giggled, straightening up and skipping over to his chair. Before he could react, she plopped down right beside him, so close her thigh pressed against his. "Aw, poor Onii-chan," she purred, leaning in until her chest was inches from his. Then, with a sly grin, she pressed herself forward, rubbing her perky breasts against his bare chest. The flimsy bikini top slid slightly, flashing a generous peek of her pink areola as she squirmed against him.

"M-Mio, what the—get off!" Kaito stammered, shoving at her shoulders, but his hands hesitated, lingering just a second too long. Her skin was warm and slick from the sun, and the feel of her chest against him sent his brain into a tailspin.

"Make me~" she whispered, her breath hot against his ear. She shifted again, dragging her breasts across him one more time before pulling back with a laugh. "Oops, did I get too close? My bad~"

"Your bad?!" he roared, leaping up from the chair and stumbling back. "You're trying to kill me, aren't you? That's your evil plan!"

Mio rolled onto her stomach on the chair, kicking her legs up and giving him another eyeful of her thong-clad backside. "Kill you? Nah, I just wanna play~" She reached back, tugging at the bikini strings like she might untie them, then flashed him a devilish smirk. "Unless you're scared you'll like it too much."

Kaito's face was a furnace, and he turned away, muttering curses. "I'm going in the pool. Maybe I'll drown and escape this nightmare." He stomped over to the edge and cannonballed in, the splash a welcome distraction from the chaos Mio was unleashing.

But Mio wasn't done—not by a long shot. She hopped up and followed him, diving into the water with a graceful arc that made her bikini flutter like it might slip off mid-air. She surfaced right in front of him, hair plastered to her face, water streaming down her body. The bikini clung even tighter now, the wet fabric turning semi-sheer and outlining every curve.

"Miss me, Onii-chan?" she chirped, swimming closer. She splashed him playfully, then ducked under the water, popping up so close her chest brushed his again. "Oops, slippery in here~"

"Back off!" he barked, splashing her in retaliation, but she just laughed and splashed him back. The water fight escalated, and soon she was darting around him like a mischievous mermaid, "accidentally" bumping into him at every turn. Each brush of her body against his—her breasts grazing his arm, her hips nudging his side—chipped away at his sanity.

Then came the killer move. Mio climbed out of the pool, water cascading off her as she stood on the edge. She shook her hair out, droplets flying, and turned to face him. "Hey, Onii-chan, watch this!" she called, then bent over to adjust her bikini bottoms, giving him a front-row seat to her ass cheeks jiggling as she tugged the thong back into place. She straightened up, hands on her hips, and "adjusted" her top next, lifting it just enough to flash her boobs for a split second before letting it snap back down.

Kaito sank under the water, bubbles erupting around him as he groaned internally. She's trying to murder me. That's it. Death by teasing. When he resurfaced, Mio was back in the pool, swimming up behind him and wrapping her arms around his shoulders.

"Gotcha~" she whispered, pressing her chest against his back. "You're so fun to mess with, Onii-chan. Bet you're dying to touch me, huh?"

"Get off me, you demon!" he yelled, flailing to shake her loose, but she clung tighter, giggling like a gremlin. Her breasts squished against him, the strings of her bikini tickling his skin, and he could feel every inch of her pressed up close.

"Aw, don't be shy," she teased, sliding around to his front and floating there, her legs brushing his underwater. "I could make it even more fun~ Wanna see me untie this top? Bet you'd faint."

"I'd rather drown," he growled, shoving her away and swimming to the ladder. He hauled himself out, dripping and fuming, and grabbed a towel to wrap around his waist. "You're insane. I'm done."

Mio pouted, floating on her back with her chest thrust upward, the bikini top barely holding on. "Boo, you're no fun! Guess I'll just sunbathe then~" She climbed out, grabbed a towel, and stretched out on a lounge chair, arching her back so her boobs and ass were on full display. She peeked at him through her lashes, smirking. "Sure you don't wanna lotion me up, Onii-chan?"

Kaito stormed toward the house, towel clutched tight. "I'm locking myself in my room. Don't follow me!"

Her laughter followed him all the way inside. "See you later, Onii-chan~ Sweet dreams!

********

Kaito thought he'd escaped, but Mio wasn't about to let the day end so easily. After a few minutes of hiding in the house, guzzling water and trying to erase the mental image of her wet bikini body, he heard the glass door slide open again. He groaned, knowing what was coming.

Sure enough, Mio strutted back in, still in that ridiculous string bikini, now holding a bottle of sunscreen. "Onii-chan~" she called, her voice dripping with fake innocence. "I need help. I can't reach my back!"

"Then burn," he shot back, not even turning around from where he stood at the kitchen counter.

"But I'll get all red and peeling!" she whined, skipping over to him. She thrust the bottle into his hands and spun around, pulling her twin-tails aside to expose her bare back. The bikini strings dangled there, taunting him, and her skin glistened with a mix of pool water and sweat. "Pretty please? I'll be good~"

Kaito stared at the bottle, then at her, his resolve crumbling under the weight of her pouty stare. "Fine," he muttered, squirting some lotion into his hands. "But don't make it weird."

"Me? Weird?" She giggled as his hands met her skin, spreading the lotion across her shoulders. He tried to keep it clinical—quick, efficient, no lingering—but Mio had other plans. She arched her back, letting out a soft, exaggerated moan. "Ooh, Onii-chan, your hands feel so good~"

"Cut that out!" he snapped, smearing the lotion faster, but she kept squirming, making it impossible to avoid brushing the strings of her bikini. His fingers slipped once, grazing the side of her chest, and she gasped dramatically.

"P-pervert! Did you just cop a feel?" she teased, spinning around to face him, her boobs bouncing with the motion. The bikini top shifted again, flashing a peek of nipple before she "fixed" it with a smirk. "Naughty Onii-chan~"

"I didn't mean to!" he yelled, dropping the bottle like it was cursed. "You're the one moving around like a damn snake!"

Mio laughed, stepping closer until she was pressed against him again, her chest squishing against his. "Aw, don't be mad. I liked it~" She grabbed his hands and placed them on her hips, right where the bikini bottoms tied. "Wanna lotion my front too?"

Kaito yanked his hands back like he'd been burned, stumbling into the counter. "You're a monster. I'm not doing this."

"Suit yourself~" she chirped, grabbing the bottle and squirting some lotion into her own hands. She started rubbing it onto her chest, slow and deliberate, her fingers slipping under the bikini top to "adjust" it, flashing him again and again. "Guess I'll just do it myself… unless you wanna watch?"

"I'm leaving!" he declared, but his feet didn't move. He was rooted to the spot, torn between fleeing and the stupid, traitorous part of him that couldn't look away.

Mio finished with her chest and moved to her thighs, bending over right in front of him to slather lotion on her legs. The thong bikini rode up, exposing her ass cheeks fully, and she glanced back with a grin. "Sure you don't wanna help? I'm all slippery now~"

Kaito bolted. He made it halfway up the stairs before she called after him, "Onii-chan, wait! I need you to tie my top tighter—it's slipping!" He didn't stop, locking himself in his room and collapsing on his bed, face buried in a pillow.

Downstairs, Mio smirked to herself, lounging on the couch with her lotion-slicked body. "He'll crack eventually," she mused, plotting her next move. "Maybe I'll 'lose' my bikini top in the pool…"

******

The next hour passed in tense silence—Kaito hiding in his room, Mio plotting downstairs. But the heat was relentless, and eventually, he caved. He needed the pool again if only to dunk his head and clear his thoughts. He grabbed a fresh towel and crept back outside, hoping she'd gotten bored.

No such luck. Mio was back by the pool, lounging on a floatie in the water, her bikini somehow looking even skimpier now that it was dry and clinging to her sun-warmed skin. She spotted him immediately and waved. "Onii-chan! Back for more~?"

"Shut up," he grumbled, tossing his towel onto a chair and jumping into the deep end. The cool water was a relief, and for a moment, he thought he might actually relax.

Then Mio paddled over, her floatie bobbing as she leaned forward, giving him a clear view down her top. "Wanna play a game? How about Marco Polo… but if you catch me, I'll let you untie one of these strings~"

"No games," he said flatly, swimming away. But Mio ditched the floaties and chased after him, her giggles echoing across the water. She caught up fast, wrapping her arms around his neck from behind and pressing her chest against his back again.

"Caught you first~" she whispered, her lips brushing his ear. She squirmed against him, her boobs rubbing up and down his spine, the bikini strings tickling his skin. "Feel how soft I am, Onii-chan?"

"Get off!" he roared, twisting free and splashing her in the face. She sputtered, laughing, and splashed him back, starting another water war. This time, she got creative—diving under and popping up right in front of him, her chest slamming into his as she "lost her balance."

"Oopsie~" she giggled, clinging to his shoulders. The bikini top slipped again, flashing both boobs for a full second before she "fixed" it, smirking all the while. "Guess I'm too slippery for you to handle."

Kaito shoved her away, his face a tomato. "You're doing this on purpose!"

"Duh~" she shot back, swimming circles around him. She ducked under again, and this time, when she surfaced, she shook her hips underwater, sending ripples through the pool. "Wanna see me twerk again? Bet it looks even better wet~"

"No!" he lied, but she did it anyway, climbing onto the pool steps and twerking right there, water streaming down her body as her ass cheeks bounced. The thong bikini was useless, sliding to one side and flashing everything before she tugged it back with a laugh.

"Oops, wardrobe malfunction~" she teased, turning to face him and cupping her chest, jiggling her boobs for emphasis. "Guess this bikini's too small for all this~"

Kaito sank under the water again, screaming internally. She was relentless, a tornado of lewd chaos, and he was drowning in it—figuratively and maybe literally. When he came up for air, Mio was back in the pool, floating on her back with her legs spread just enough to make him choke.

"Wanna swim between my legs, Onii-chan?" she called, kicking playfully. "Plenty of room~"

"I'm done," he declared, hauling himself out of the pool and stomping toward the house. "You win. I'm dead. Happy now?"

Mio laughed, rolling off her floatie and swimming to the edge. "Very happy~ See you Onii-chan! I'll wear something even skimpier!"

******

Kaito tried to stay inside, but the heat—and Mio's incessant knocking—drove him back out. She'd dragged him into another sunscreen session, this time insisting he do her legs. He knelt by her chair, hands trembling as he rubbed lotion into her thighs, her skin slick and warm under his fingers.

"Lower~" she purred, spreading her legs slightly so he had to brush the edges of her bikini bottoms. "Don't miss a spot, Onii-chan."

"You're the worst," he muttered, but he kept going, his hands slipping closer to dangerous territory. She moaned again, louder this time, and he dropped the bottle, bolting upright. "That's it. I'm out."

"Aw, but you're so good at it!" she called, rolling onto her stomach and arching her back to flash her ass again. "Wanna do my cheeks next?"

He didn't answer, just stormed back to the pool and jumped in. Mio followed, and soon they were locked in a game of chase—she darting around, flashing him at every turn, he pretending to hate it but secretly memorizing every jiggle and sway. She'd "accidentally" untie her top, letting it float away before snagging it back with a giggle. She'd twerk against the pool wall, her ass cheeks bouncing in his face, then swim off before he could yell.

By the time the sun started to set, Kaito was a wreck—exhausted, flustered, and dangerously close to admitting he loved every second. Mio lounged by the pool, bikini still intact (barely), smirking at him. "Best day ever, right, Onii-chan?"

He glared at her, towel wrapped tight. "I hate you."

"Love you too~" she sang, blowing him a kiss.