This last summer I was at home, getting ready to leave to class one Tuesday morning when I heard my female 13 year-old cousin breathing heavily in her bedroom. From my room I could see she was on her bed with her covers off and had her left hand on her stomach. I had passed by her room a few times and had seen her hand on her crotch but nothing was happening, it was just placed there.
So I was listening to this breathing and decided to look and after a few seconds of watching I saw her rub herself through her little shorts. She went up and down her pussy about 10 times I'd figure. I had a robe on because I had just been showering and my boxers and had a huge boner.
After she'd finished rubbing herself I thought that was it and left to school but couldn't concentrate on anything because I just had that image in my mind. The most penetrating thing about it was how vulnerable she was at that moment. It still blows my mind, the mere fact that we humans do this self pleasuring thing. It's a wonderful thing.
Since that time I had often fantasized about what I'd like to do with/to her. She's really sexy but is my cousin and is thirteen. Even so, I fantasize about her a lot.
We flirt here and there and happen to rub each other some times.
I've listened to her masturbate in bed numerous other times and confronted her about her masturbation but she's a bit reluctant to talk about it. I recently read a story here where a boy learned to sniff his cousin's panties and I tried that and found great treasure in hers. Her jizz is all over her panty's. She really goes at herself when she masturbates. They smell so great.