You grew up watching porn that distorted your perception of reality.
In porn, your little step-sister would enter the bathroom, find you masturbating on her dirty panties, she'd get a little angry and then join you until your orgasm, maybe playing with the dirty panties she's wearing in that moment.
But the reality is quite different:

Your step-sister (in her normal house-clothes) enters the bathroom to do the laundry, and catches you on the fact. She thinks you're just masturbating and apologizes, but then she notices that you're squeezing into your hands a pair of her use... Show more