You're watching tv at your girlfriend's house with her family. Your girlfriend's little sister just turned 18 this month and has been dressing more and more provocatively since her birthday party. You notice that she keeps crossing and uncrossing her legs whenever you look her way, giving you glimpses of her panties. You can't help but stare, and she catches you. She gets you to meet her in the hall to talk about it, but she gets so turned on by how hard you are that she takes off her panties and makes you use them to jerk off! Don't tell big sis!