Your girlfriend turns into your sister.

"Hmm... you do huh... so who are you going to be?" you curiously ask.

"Well, first of all close your eyes and don't ever look or peek on me until I give you a signal to open them." Your girlfriend exclaims as she signs you to close your eyes.

"What kind of signal?" you ask.

"When I'm going to kiss you on the lips." your shapeshifting girlfriend smiles with her flirtatious attitude and gives you a cute wink at you. "Anyway, please closes your eyes so I can change myself, hun."

"Okay, babe. Whatever you say." you reply to her as you close your eyes and wait for her to give you a signal. Then later, while you closes your eyes without open them yet, you feels your girlfriend's mouth is kissing your mouth as she gives you a signal to open them. As you open your eyes and see your shapeshifting girlfriend in front of you just morphed herself into your own bratty sister, a high-school bitchy girl and captain of the cheerleading squad, in her naked body showing off her hourglass shape and pair of D-Cup breasts. "Like, what do you think, bro? Do I look pretty cute to you." she asks with her flirtatious attitude and her new high-pitch, bitchy voice that sound exact same as your sister did.

"Is that still you, babe?" you ask just to make sure.

"Of course, it's still me, bro. I'm not like, your real sister, y'know. But anyway do you, like, want this to be a role-play or not?" she said as she's also behaving exactly like your real sister too! You thought yourself that your shapeshifting girlfriend just mentally change herself. Yet, when looking into those ocean blue eyes you could somehow still tell it was her. "Teehee, what's wrong with you, bro. You just, like daze off when you see me like this." your girlfriend in your sister's body says as she sits on your laps and hug you.

"Err... sorry, sis... I mean, babe. I...I was just-"

"It's okay, bro. You can like, call me 'sis' if you want to. So are you going to, like, do anything with me or are you being like, a total dweeb?" your shapeshifting girlfriend asks as she's moving her hips on your cock.