I was 15 when this happened, she was 13. I was at my best friend's house for a sleepover. His parents were out of town, and his sister was at a friend's house. He (being 16, as his birthday was a few months before mine) decided to drive out and grab a few things from the store that we had forgotten earlier. I elected to stay behind.
Once he had left, I wandered upstairs to the bedrooms. I wandered into his sister's bedroom, and started looking around. I picked up a pair of panties which were sitting at the top of her laundry hamper. They were apparently a pair she had worn very recently, probably earlier that day. I felt at the crotch area, and realized that they were soaking wet with her juices. I lifted them to my face and gave them a tentative sniff. I never realized that a cunt smelled that good. I became hard almost immediately, and grabbed my cock and started to stroke it.
I looked up and saw her video camera in the corner. I knew that her hobby was making films, but... No, she wouldn't have. However, I couldn't help but look. I rewound the tape and pressed play. She appeared on the screen, wearing nothing but the panties I had in my hand, swaying her hips and pressing her surprisingly large tits together. The next scene showed her doing the same thing with a dildo before she took it into her mouth and deep-throated it. I watched in fascination as the scene changed again and showed her lying on her bed, legs spread, rubbing the dildo on her smooth young pussy. As she slid the dildo in, I heard the doorknob turn. I didn't have enough time to even cover myself up before, lo and behold, my best friend's sister appeared behind the door. She and I were both too shocked and embarrassed to say anything, but the video kept playing. I decided I had to do something, so I hit the pause button. She looked at my hard cock and said, 'Why were you watching that video of me?'
I replied that, 'I was watching your video because you're really sexy.'
She blushed and turned away, saying, 'No, I'm not. All the girls at school say that I'm fat and ugly.'
She sat down on the bed next to me, and I said, 'No you're not. You're one of the sexiest girls I've ever met,' as I pulled her T-shirt off and unhooked her bra. Her firm young breasts bounced free, and her nipples hardened in the cool air of the bedroom. I asked her, 'Could I watch you masturbate now?' and she answered in the affirmative.
She reached under her bed and pulled out a shoe box, from which she removed the dildo I had seen her using in the video. She lay back on the bed and spread her legs as she had in the video. I saw that under her short skirt, she wore no panties. Immediately, she started rubbing her pussy with her fingers, then she started to put one, then two, then three fingers into herself, before sliding the dildo in. As she slid the dildo in and out, she licked the juices off her fingers. In a few minutes, as she was about to come, I started stroking my cock harder, and we both came at the same time, her juices squirting out onto me, and my semen all over her chest. We looked at ourselves, and realized that we needed to clean up, fast. We both jumped into the shower, and it was all we could do to keep our hands off each other as we washed our own, and each other's fluids off ourselves. We dried off and got dressed, and the next day, when I was leaving, she handed me a package, containing the tape I watched and two others, and several of her pairs of dirty panties. We met often in the future, but not for activities which this site is about.
I hope you enjoyed reading.