My cheeky adult sister casually touches my crotch, and the direct sensation makes me cum in seconds, leaving a visible stain on my pants. When she notices, she mocks my “pathetic cock” and keeps playing with it until I ejaculate again. Watching me fire repeatedly starts turning her on, completely changing the mood. The once-bratty sister softens and begins seriously craving me, turning my hypersensitive premature ejaculation complex into an unexpected advantage.