My girlfriend is a single mother with a 19-year-old daughter. I've moved into her place and we're living together. I can't help but be drawn to her daughter more than to her—because the girl has an incredibly erotic body. Even in front of me, her mother's boyfriend, she walks around braless, and her shorts often ride up, exposing her half-butt or panties. I manage to restrain myself when my girlfriend is around, but when I'm alone with her daughter, I just can't hold back anymore. Waiting until my girlfriend comes home late, I sneak into her daughter's room to indulge once again in sex with my girlfriend's daughter.