Solo Act With Girl's Panties

When I was about 15, I had a friend who had an incredibly hot 19-year-old sister. Once when I was at his house, I found a pair of her panties lying around, and so I decided to sneak them into my pocket. While a few of us were watching a movie in the dark, I put a blanket over my lap, pulled out the panties, and masturbated into them. It was exhilerating to be pleasuring myself into these panties; and while in the presence of my friends.