My sister-in-law "Mei" lives with me, and whenever my brother goes to work and we're left alone, she starts acting strangely—deliberately emphasizing her big tits and big ass. She tempts me by asking for a massage, watches me jerk off, and even shows off her sex with my brother, taking a teasing, provocative attitude. Because of her, I've been losing sleep, until finally she says, "You're all pent up, aren't you?" and starts groping my crotch.