I was 12 when this happened
Let me begin with a little background info (you might need to know some of it). I'm 13 years old, and have WAY overly-protective parents. This and being a very early starter in puberty is a bad combination. I got my period when I was 9 1/2, and have been masturbating since I was about 9 (although I didn't know that it was called that until about a year ago.) My parents haven't made any attempt to teach me anything about sex, and I don't think they plan to for a while. They think that because I am generally really good and polite, get good grades, and go to private school, I am suppossed to remain completely uninformed until I'm married. Of course, they don't know how wrong they are.
On with the story. Last December, I was invited to one of my friend's birthday party. We'll call him... Joe, for the sake of the story. Anyway, it's pretty obvious we both like each other, but we're too shy to admit it. I'm a girl, but I like video games and stuff like that, so most of my friends are guys. Joe, who I've been really good friends with since 3rd grade, was having his 12th b-day party at his house. It was a sleepover, and he was inviting 4 guys from school, and also really wanted to invite me. Of course, us both having overly-protective parents, they both said NO at first. After a little begging on his part, his parents finally agreed and then so did mine (surprise to both of us). Besides, all we planned to do was play video games, eat dinner, more video games, cake, his dad (who used to be a pro magician before he was a doctor) do a magic show, more video games, movies, sleep, more video games, breakfast, and more video games. So, when I got there, all but 1 person was there, and so we let the gaming marathon commence. Before we knew it, it was time for everyone to change and put out the sleeping bags. His parents made us stay in the living room (right ouside their room) the whole time, even though they said they trusted us all. I rolled out my sleeping bag, and so did everyone else. He ended up next to me. So we all went to different bathrooms to change, and then all gathered back in the living room. Suddenly, he said he was going to his room for a second, and to not come upstairs. I thought that was odd, becuase he said that to everyone, not just me (the only girl there). Soon, everyone else decided to go up and see what he was doing, so I just followed along. Little did I know what was about to happen. We all crept up the stairs, and we heard these weird moaning noises coming from his room. We all slowly opened the door, and there he was, lying on his bed, stroking his cock and moaning. God I wanted to masturbate so bad, but I knew everyone would know what I was doing. So we went downstairs, and got Monty Python ready to watch, until he came downstairs. I noticed he was still kind of hard and there was a small wet spot on the front of his PJs. We carried on as if nothing happened (and as far as he knew, nothing did happen), wathced 2 movies and played ps2 until 3 AM (his parents were asleep). After all my friends were asleep, or so I thought, I still remembered what I had seen and began to masturbate in my sleeping bag. Normally I don't really fantasize while I masturbate, but I found out that it made it so much better when you do. I was getting pretty close to orgasm, when I felt a hand on my breast (remember, I was a very early starter, so I have pretty big boobs for my age). I stopped and looked over, and saw that Joe was awake, and moving his other hand towards my wet pussy. Even in the dark, I could see his face turn dark red when I looked over at him, but he kept on going. It felt so good to have someone else masturbating me, I almost screamed (that would be a pretty scene: I scream, everyone wakes up, including his parents, they all see us, and I never leave my house again.) Suddenly, he pinched my clit, sending me over the edge into the best orgasm I've ever had. Afterwards we acted like nothing happened, but I still love remembering that time.