"Hey, bro. I'm home, are you still- OH MY GOD, WHAT ARE YOU GUYS DOING!?" your REAL sister now already home as she opens the door and shocks as she's spot you both are having sex on the sofa.
"Oh my god, sis. Y...you're... home..." you both shock and stress out a lot as you saw your REAL sister enter the home without notice, plus when she enters the house she saw your shapeshifting girlfriend your own sister's clone. The shock of the situation leaves your sister frozen dropping her purse to the ground with her jaw almost dropping as far. "Bri... what is going on? Who is she and why is she look exactly like me?" your REAL sister asks still frozen in front of the door.
“Uuuhhh.... Sis. I swear I can explain this situation.” you say nervously.
“We like, can explain this.” your shapeshifting girlfriend states still as your sister as she gets out of the bed fully naked.
"Who... what...?" your sister too overwhelmed at the site of seeing her twin self collapses in a heap on the floor. You hastily get dressed quietly screaming at your GF. "What do we do now?!"
"Well, let's take her to her bedroom and let me think." Your girlfriend says as she gets dressed. After a few minutes she’s come up with that the only way to play it off is to tell her about the shapeshifting. She’d probably go crazy if you didn’t and maybe she’d be interested in some things. When your sister comes to she asks again what is going on. “Well, hey there. I hope you still recognize me, it’s me your brother's girlfriend and I’m secretly a shapeshifter.” She says as she morphs into her own body.
“What? Is that really you? Why you were 'ME' then and why did it look like you were screwing each other earlier?” your sister inquires.
“Well sis, I’ve always found you quite cute, but still a bitch like a bimbo slut, and when my girlfriend offered to become anyone I dreamed of I couldn’t pass it up.” You state bashfully ad your sister blushes.
"Oh my, I haven’t heard someone compliment me like that it some time. I’m frankly a little flattered, bro." your sister says.
Your girlfriend shocks by her reaction says, "That’s great because for my sake I’m gonna need you to keep this between us."
"Of course, I will. I wouldn’t want anyone to expose you to the public." your girlfriend says.
"Good girl." you pat your sister's head.
"But y'know, I've been wondering if you guys don't mind can we do something for fun with each other?" your sister asks.
"Of course, girl. Anything, what do you want to do?” your shapeshifting girlfriend asks.
"Well I was thinking if...