hiii thanks so much!! i'm rly happy to hear that.. idiosyncrasy is one of my favorites too! i hope this one's to your liking too ^_^

They were only supposed to go to the beach. Minako promised they’d just go to the beach with the rest of their friends.

Well— her friends, really. They were mostly girls whom Minako befriended during their first year of middle school. Because they were friends with Minako, that made them Minato’s friends by extension. That’s what she insisted, anyway. Minato didn’t really care. He had his sister and that was all he needed at thirteen years old.

Except she liked to say one thing when she really meant the other, at times. He wouldn’t go so far as to call it lying, because he should really be smart enough to realize when his sister is up to something. Minako had a knack for getting into trouble and dragging her brother into it, too. That’s how they’d always been, since they were little and their parents were still around up until now, being passed on from auntie to uncle to auntie.

Earlier that week, she said they’d go to the beach.

“It’ll be fun!” said Minako, tugging at his sleeve as he tried to focus on his homework, “C’mon, all you do is stay inside and play games all day.”

“I like staying inside and playing games all day,” said Minato, “besides, I can’t go into the water.”
His sister frowned. “You can still come with us. Just stay on the shore with our stuff.”

“I don’t wanna babysit your stuff.” He was half-way through writing an equation down before scribbling off the page, Minako’s hands tickling at his sides. Minato’s attempt to push her away was weak as he giggled, “Hey, don’t!”

She had him pinned to the floor and in tears by the time he pried her hands away. He was still gasping for breath as she asked, “Please come with me, Mina?”

Minato sighed, and loosened his grip on her wrists. Minako slid her hands down until they were palm to palm, fingers threading through his like silk. His heart did a little flip as he watched, cheeks flushing as warmth bloomed through his chest. These odd sensations and feelings were commonplace to him ever since they entered middle school and Minako had begun growing into herself and Minato had begun falling behind.

“I’ll go with you,” he acquiesced, “but I’m staying on the shore. And I’m wearing a shirt.”
Minako dipped down to kiss the tip of his nose. “Yay! It’ll be so much more fun with you there, Mina. I promise!”

Fun wound up involving a sneaky trip to the showers. Fun wound up to be what they typically got up to at night under the covers, except Minako had to make it so much worse.

The bikini she brought for him was, unsurprisingly, a perfect fit. She knew his body as well as her own, by now. Of course she would know what size would fit him best.

His hands itched to rip it off. The bow she tied on his back was too tight and the bikini bottom hung too low on his hips. It accentuated the dip of his bones, how skinny his thighs were and the curve of his waist towards the small swell of his chest. It pointed out his lack of flesh in comparison to his sister, who filled out her own swimsuit nicely.

He didn’t have any time to appreciate it, though. Minako pulled him into one of the shower stalls just to have him try this pink, frilly thing on while her friends continued to play at the beach.
“Oh, you look so cute,” she giggled, pulling him close by the waistband of his bikini bottom, “you really should wear this out.”

Minato pushed at her wandering hands as he turned his head away. Minako had tried for a kiss but ended up pressing her lips to his cheek, instead.

“I wore it,” he said, “I wore it, so… let’s go back, please?”

“Why are you in such a rush? They won’t miss you.” Minako shifted from his cheek to his jaw, pressing kisses against his flushed skin until he shuddered under her. With a little push, his back met the wall of the shower stall and he was caged in place. “I told you we’d have fun. I know this is your favorite thing to do.”

Her hands were too hot on his body. They traveled the expanse of his torso, tracing over his ribcage and down towards his navel. One of her hands brushed over his belly button and he sucked in a breath. Fingers teased at his waistband while her lips found his collarbone.

“You’re wrong,” Minato’s voice came out too shaky and too uncertain, “I don’t like this.”

Her laughter was candied. Sweet as it filled the empty shower room. Minato typically loved the sound— when it wasn’t being directed at him.

Minako's nails closed around his nipple and rolled it between her fingers. He willed himself to stay still, to ignore the brief sparks of pleasure from the pain and swallow back his moans. Minako couldn’t get her way this time. He would deny whatever reaction she wanted to pull from him for as long as it took.

His sister pouted as she looked up at him, pretty eyes narrowed. “Don’t be like that. I like hearing you.”

“We shouldn’t be doing this, Minako,” he tried, “We could get caught.”

“Duh. That’s what makes this even more fun.” Her hand slipped under his bikini bottom, diving right for her goal. The pad of her finger found his clit and he couldn’t smother the whine from his mouth fast enough. She simpered at his reaction. “See? You still want this. You always want this.”

“I don’t, I—” She pressed hard against him, delighting in the broken moan that left his throat. Minato pushed at her shoulder, nails digging into the smooth skin. “Minako, please—”

“You don’t have to beg,” His sister kissed him at the same time her middle finger slipped into his cunt, swallowing the moan that spilled from his mouth like water, “I’ll give it to you.”

It really was awful. She was awful, and Minato knew he couldn’t keep coming up with excuses for her behavior forever. He couldn’t keep scrambling for reasons as to why his sister should be allowed to play with his body like this, pushing him hard against the wall to get a better grip so she could move her wrist faster, harder. His head hit the back of the wall hard as he grit his teeth to smother the whines and keens that left his throat, pulled out from deep within his diaphragm.

Minako knew his body as well as her own by this point. She had the same parts as he did, after all, she just knew how to play with them better than he ever could. Being twins, their body types were considerably similar. Identical down to the beauty mark on their hip.
So of course her pleasure points would be his. It only made sense.

“We can’t,” he gasped, pushing against Minako’s shoulder, “We should stop— we should stop doing this, Minak-oh— please—!”

Minako spoke as if reprimanding a disobedient pet. “You keep saying ‘no,’ but you’re this wet. You’re even more wet than usual.”

He shook his head, refusing to look down and acknowledge the slick running down his thighs straight towards the floor. Something just felt— different. A strange sensation as if something were building, coiling tight inside of his belly alongside the pleasure. It was going to come out if she did this any longer, whatever it was. Fear suddenly spread through his body like a virus.

Minato really did try to push her hand away and out of his bikini. She would laugh at him if that happened. He’d never hear the end of it. “Stop, don’t do that, something’s…”

“What?” asked Minako, innocently enough, “Here?”

She went straight for the spongy spot inside of him, someplace Minato hadn’t really been able to reach himself because he could barely stand having his own fingers inside of him. A sob broke from his throat, tears beginning to gather and blur his vision. “Stop!”

“What happens when I do this?”

Minako had no trouble flexing her fingers, rubbing and rubbing and rubbing until he had to scramble to push her hand away. His hips went taut and the pressure building in his belly seemed to burst, hitting the shower floor in streams.

It was the worst kind of release, worse than cumming, worse than anything Minako could have done to him. His sister yanked her hand back with a gasp, leaving Minato to cling to her as his hips twitched and legs shook. It left him dripping and more foggy-headed than before, panting for breath against her neck.

“You— did you—?” Minako seemed to struggle to find the words to say, caught between laughter, “Did you just pee? From that?”

Had he? He wanted to deny it. He couldn’t have. That couldn’t have made him— was that even possible? That hadn’t happened before when they did this, it felt just as visceral and raw as it usually did, only worse. So much worse. He could hardly keep himself up with the amount of pleasure drowning his senses out, robbing his ability to speak. He wanted to say no.

But Minato’s mind had run away from him at the same time that mess burst out of him and he didn’t have the energy to chase it back. His sister sounded so amused, like Minato just showed her a neat party trick. Her laughter rumbled in her chest, vibrating against his cheek and he wanted to hide away in the sound. Burrow deep inside her chest so she wouldn’t be able to touch him again but he could still be safe and sound. Minako always kept him safe and sound, didn’t she?
Even when she was being mean, like now. Minako’s laughter dissolved into giggles as she held Minato close. Her lips found his cheek with a loud smack.

“You’re so much fun to play with, Mina,” his sister said, “I wanna see what else I can get you to do.”

Distantly, he thought of her friends still back at the beach. He wondered if they even noticed the two of them were gone. They were supposed to be there with them. Minato said he’d watch their stuff.

Instead, he let Minako kiss him again, weak against her eager lips and tongue. All of him was weak for her.When her hands found his hips to pull his bikini bottom off, he didn’t even flinch. She was saying something about returning the favor, guiding his hand to between her legs, and he dropped to his knees in response. Her pleasure was his.