My girlfriend is a single mother with a 19-year-old daughter. I've moved into her place and we're living together. She's 40 years old, but she's constantly worried about her stepdaughter—because the girl has an incredibly sexy body. Even in front of me, her boyfriend and her mother's partner, the daughter walks around braless, often wearing short shorts that expose half her ass or glimpses of her panties. I try to hold back when her mother is around, but when I'm alone with the daughter, I can't control myself. I wait for nights when the mother comes home late, then sneak into the daughter's room. That's when I indulge in a forbidden, erotic relationship with my stepdaughter.