I would never betray my girlfriend. I would never cheat on her! Even if you act like a saint, what if your girlfriend's older sister is a beautiful, outgoing woman with an amazing body, who is a kiss-freak when she gets drunk, and is a pervert who shows off her big breasts and aggressively seduces you...? Who could resist that? She says she has a boyfriend, but... she's just a hopeless slut!