My little sister always wears my clothes without permission. She's the complete opposite of me, a big guy. When I saw that she was wearing my shirt again, I took a second look and saw that she was not wearing a bra! What's more, she wasn't even wearing any pants, so her underwear was completely visible! I was shocked, but I got an erection. When my little sister noticed the strangeness of my lower body, she suddenly started to fidget... Although we hadn't felt any sexual attraction towards each other until now, the atmosphere suddenly became erotic and we finally crossed the forbidden line!