A Young Voyeur's Pervy Adventures/Day1/Yes, remove your trunks
You turn around, thumbs in your waistband.
It was still a little awkward, stripping in front of your sister, but it was manageable so long as you faced away from her. You peel off your trunks, wring the water out of them, and toss them outside the show so they wouldn't get soaked again. When you turned back to Wanda you keep your hands at your sides, leaving your semi-erect penis exposed.
"Glad to know you're so comfortable around me," she said with a smile and quick glance downwards.
As she spoke she put her hands behind her head to smooth back her hair, pushing her boobs out towards you just like before. Seeing this reminded you of the fact that your barely clothed sister is mere feet from you with only a few small pieces of fabric hiding her body.
The reaction was immediate. You felt your penis start to harden completely, and you weren't the only one to notice as Wanda stared, slightly open-mouthed, at the sight. There was an awkward pause before Wanda let out a sudden laugh, causing you to jump.
"Hehe, okay then. I guess it's also good to know that at least one boy finds me attractive!"
The wave of embarrassment you feel is quickly stifled by the friendly smile from your sister. You smile back and laugh with her, but also notice how she briefly rubbed her thighs together as she changed position. From there you had a normal, albeit quicker than normal, shower as you washed off the rest of your body. At one point your erection brushed against Wanda's butt, causing you to panic as you worried she would get mad, but as if reading your thoughts she started massaging your scalp again to calm you down.
Before long you were done and stepping out of the shower. Wanda, however, held back.
"Oh Matt~" she said in a playful voice.
"Yes?"
You turned to face Wanda, who was leaning past the half-open glass door. She had a funny smirk on her face, as if she was aware of some joke you didn't know about.
"Remember what I said about a reward for good behavior?"
"Um, yes?" you say skeptically.
"Well wait right there."
She ducked back behind the frosted glass and, to your utter astonishment, began uniting her bikini. First she undid her top, then the two ties to her bottoms, leaving her blurry figure totally nude as she wrung the water from them. You stood there dumbstruck as she leaned back into view, her entire top half unobstructed by the glass with only one arm covering her ample boobs.
"Catch," she said, tossing her bikini to you with her free arm. Still processing that your sister just willingly got naked in plain view, minus the glass, you failed to react to the flung swimwear, the top draping across your shoulder as the bottoms humorously caught themselves on your rock-hard penis. Wanda let out another laugh before speaking.
"Well, here's your reward! Enjoy it as long as you like, as much as you like, but no peeking!"
She pointed at you to emphasize her last point, but quickly replaced it with a smile before sliding the door shut and returning to her shower. By this point your erection was to hard to bare, and despite your desire to stay and enjoy the view you grabbed your shaft and started pumping. The fact that she's right in front of you, her body blurred yet very obviously naked, and that she knows you can see her excite you in ways you didn't think earlier.
Your breathing gets harder. From behind the frosted glass you see her moving her arms, running them up and down her body, over what must be her boobs. You imagine how she must be standing there, rubbing and squeezing them. You think of how she stood in front of you mere minutes ago, only one arm hiding her bare breasts as she smiled at you, undoubtedly knowing exactly where you were looking.
Humming filled the bathroom as Wanda continued her shower, and you could feel yourself getting closer to relief. Right before you do, however, you realize that you're about to spray cum all over the floor. You grab the first thing you can think of to cum into.
Wanda's bikini bottoms.
You let out a quiet grunt as you climax into the black material, too quite for Wanda to hear over the water and her humming. A twisted thrill briefly runs through you at knowing that you're ejaculating into something that was pressed right against your sister's most intimate area not to long ago. You stand and gaze at Wanda's figure as you enjoy the blissful feeling pulsing through you with every twitch of your penis.
Unfortunately the feeling fades far too quickly, leaving you standing there with a pair of cum-soaked bikini bottoms gripped around your cock. Realizing how embarrassing it would be to get caught like that, you pull the bottoms off your penis, being extra careful not to let your cum dribble to the floor. Setting that and the top aside you dry off quickly and pull you trunks back on. Wrapping the soiled bikini in your towel you grab the handle, but pause, turning back to the shower.
"Hey Wanda?"
"Yes Matt?"
"Um, t-thank you for, um, you know..."
"It's no problem. After all, it was your reward," she replied. As she spoke you could see her blurry, naked profile, and even now, so soon after you just came, you feel a twitch in your trunks at seeing her bare curves.
You leave the bathroom and head for your own room, a happy smile plastered to your face.
Wanda is the best.
What next?