Squats at the gym.

Megan throws the pink nike short shorts she was going to wear at you and goes to her room for more panties and shorts.

You're intimated by your sister cause she's so fit and serious about working out. And she did just catch you red handed sniffing her most intimate spot.

You reluctantly pull up her panties up over your cage then the shorts she threw at you. Not only do you have a huge whale tail from her sexy g-string but the shorts slide right between your cheeks. You never felt so much fabric between your cheeks. Aching in your cage and turned on from your sisters clothes, your dick dribbles pre-cum from your cage into her panties.

Your sister walks back in "you ready to go?" You stumble for a sec. Yeah I guess. She tosses a blonde mid length wig at you. "Put this on. I don't wanna be seen with you" putting the wig on, you look into the mirror looking like any other girl trying to show off her butt at the gym. "Lets go"

Driving to the college gym your sister uses, the car was dead silent. You had nothing to say. Your heart pounding at the excitement and embarrassment that you actually liked the way you looked.

Squats at the gym started, all the guys staring at your ass. "Don't worry bout them. This place is the best to show off your ass and take instagram pics"

After what felt like hours you could feel your cheeks independently move when you walked; the g-string and short shorts helping your cheeks glide. As you finish your final set, your butt flexing and trembling, Megan snaps a selfie with your butt.

What are you doing Megan? I don't want people to see my ass on the internet. "Don't worry you actually look like a sexy girl. Besides I labeled it as 'at the gym with my new bestie.' Look! Already got some comments about how good your ass looks"

Ugh, fine. Can we just shower and go home?