Prompt: “Oh, come on, you’ve seen me in a bikini before, how is this any different?”

“Oh come on, you’ve seen me in a bikini before, how is this any different,” you sister scolded, pulling off her dress.

You tried not to look, but your eyes couldn’t help as she turned. Her thin, athletic frame, plump ass. It was different. Her black bra pushed her tits out, and the thong she wore framed her butt magnificently.

“Are you coming?”

Your attention was pulled back to your girlfriend, giggling and likewise undressed. Her jeans and shirt in a pile at her feet. Like your sister, she wore a thong, but wasn’t quite as fit, her heavy chest bouncing with each step. Pushing past any awkwardness, and hiding your half aroused prick, you pushed off your own jeans, and peeled out of the t-shirt you’d been wearing. Even though it was dark, you could see both of them clearly in the moonlight, and your sister’s boyfriend, Mark following closely. You followed too, stepping over the short wall and into the hot water.

“I can’t believe this place had a hot tub,” your girlfriend giggled, leaning towards you, kissing you deeply.

She was drunk, but so were you. It had been nothing but champagne and shots since getting checked in. Her tits pressed against your chest, and your growing prick became impossible to hide against her thigh. Her eyes went wide as she felt you, her fingers sliding down to grip your cock through your thin boxers.

“What’s this?” she giggled, giving you a squeeze.

“What’s what?” your sister questioned, her back pressed against Mark.

“Oh nothing,” she answered for you, face slightly red.

She turned, her hand staying, gripping gently at your crotch as she laid back against you. Looking down you could see her massive tits bobbing gently in the water, and looking across you could see Mark looking too. Normally you might have said something, him checking out your girlfriend, but your eyes had already moved on to your sister’s chest. Her nipples poking obviously through the wet material. Perfect, gorgeous tits just like the rest of her. You had always noticed your sisters looks, but now, half dressed with her, it was all you could notice. The hand squeezing your cock didn’t help either. It could feel every twitch and pulse, and teased you more.

You couldn’t resist sliding your hand between her legs too. Your girlfriend let out a little giggle as you slide under the waistband of her thong, teasing the folds between her legs. She was hot, excited just like you. Even with your fingers exploring between her legs, your mind wandered, and your eyes peered through the rippling, bubbling water, between your sisters.

Mark’s hand was already there. Your eyes went wide as you notice, quickly looking up, you caught your sister’s gaze who was already looking at you. She watched you intently, biting her lip.

“Something about hot tubs always puts me in a mood,” she giggled.

“Mmm me too,” your girlfriend agreed, almost moaning the words.

Her hands were already pulling your underwear to the side, gripping your bare prick, nudging it between her legs. You stayed quiet, letting it happen, your cock throbbing as you felt her pull her thong to one side. You tried to keep a straight face as you felt her sink down, sliding you into her eager, warm folds. You watched as Mark’s fingers moved in small, quick circles between your sister’s legs while your girlfriend moved slowly in your lap. Your eyes moved up slowly, catching your sister’s gaze again. She smiled at you, watching with a devious little smirk.

“Mm babe,” your girlfriend softly moaned.

“You two are so bad,” your sister teased softly.

Leaving Mark, she moved closer through the steamy water. Licking her soft lips again, she leaned in, kissing your girlfriend on the neck, on the cheek, and then finally her lips.

Is this really fucking happening, you think, already overwhelmed by your girlfriend’s eagerness, her tight slit griding against you.

Moaning, your girlfriend kissed her back, there tongues intertwined as your sisters eyes watched yours. Her beautiful eyes, locked with yours as she kissed the woman you were buried inside of. Her hands explored too, squeezing your girlfriend’s chest gently, teasing her. As their lips finally separated, your girlfriend moaned, loudly and obviously. You could feel her hole pulsing around you as she started to bounce.

“Oh god, I feel so good. Babe,” she groaned, thrusting against you as she gyrated in bliss.

“Unsnap her bra,” you sister commanded, her eyes still locked on yours.

“Uhh,” you hesitated, grunting. Your brain was foggy, but did you really want to expose your girlfriend?

“Don’t be a tease, she’s gorgeous,” your sister pushed, grinning.

Reaching up slowly, your fingers found the snap, undoing the clasp, letting her huge chest free. Quickly your sister’s hands found there way to the revealed skin, teasing her nipples, and kissing her again. You watched as Mark slid his hand up, unclasping your sister’s bra too before moving back beneath the water, between her legs.

Without hesitating, she slid out of her bra, tossing it to the side as she teased her small, pink nipples. Compared to your girlfriends giant areola and massive chest, they looked delicate, delectable. You couldn’t help but stare, your cock jumping inside your girlfriend.

Your sister grinned as she sat back, reaching between her boyfriend’s legs. Through the water, you could see his cock, free and gripped in her hand before it slowly disappeared between her legs.

You caught you sister looking back at you again.

“If you’re going to have fun, so are we,” she said breathlessly.