Twins

 

All you wanted to do was have some play time with the magic amulet.  Turn into your sister, play around with her body, maybe take some pictures, and turn back.  All you had to do was keep the amulet touching your body, and you could change back at any time.  No harm to anyone.

 

Until her boyfriend came over.

 

You didn't expect your sisters body to react the way it did.  She became so horny around him as they talked.  You didn't know that your sister was a medication controlled nymphomaniac.

 

At first you could control your twitching pussy and your urges, but for some reason the longer you were around him, the hornier you got, until you just kissed him... and that started your downfall.  You literally ripped off your clothes and jumped his cock, moaning in desire as you sucked it into hardness, cumming as you do so, then mounted him, and rode his cock until you came again and again.

 

  Whimpering in pleasure, you find yourself kneeling on the couch, and spreading your ass for his huge cock, you feel your at least 6th orgasm of the last 15 minutes...

 

As you cry out in orgasm again, you feel the chain break from around your neck, and the amulet fall between the cushions of the couch.  You feel your body pulse, and you orgasm again, knowing that now and forever you will be your sisters slutty twin.