My friend was house-sitting for a mutual friend of ours. She was around 18 years of age, and had two sisters, one 20, the other 14. He was in charge of the house for about a week until the whole family came back from vacation. He invited me over to keep him company, and I decided I would stay the night. He eventually went to sleep, but me being a night owl, stayed up for hours that night.
At around sunrise, I began to get really horny. I couldn't help but think about the panties and bras in each one of the sisters rooms. I decided to venture into one of them, which was shared by the two older sisters. I looked through their dressers and found some bras and panties. I decided it wasn't enough to get me off, so I went downstairs, where the 14 year old's room was. When I opened the door to her room, I immediately saw some clothes on top of her bed. I went in for a closer look, and to my surprise, it was a pair of panties and shorts. I examined the panties, to find they were used, having a bit of residue on them. This turned me on a lot. I eventually stripped naked, and laid on her bed. The thought alone of her sleeping on the bed I was about to masturbate in turned me on even more, and by this time, I was hard as a rock. I rubbed the used panties on my cock, as I slowly stroked it up and down. After a while of doing this, I noticed there was pre-cum all over the panties now. I kept doing that for a while, and then I took the panties to my face, where I began to smell the young, musky scent of that cute 14 year old. Doing this almost made me cum instantly, but I held it back. I gave the panties a lick, and began to think about how incredibly exhilarating what I was doing was. I turned my head, and smelled her pillow, and I could imagine her head resting on it, which made me pre-cum even more.
Needless to say, I stroked my cock for around 20 minutes, enjoying the moment. I imagined the little sister laying in her bed, and how she probably had gotten off more than once in the same bed I was getting ready to unload on. After a couple more minutes, I could bare it no longer, and I came as I licked her panties, thinking about how wet she probably got in them before she casually left them on her bed. I shot out cum so high, it hit the pillow next to my head. I laid there for a few minutes afterward, thinking about her laying on the bed I had just violated, and it turned me on even more. I put my clothes back on, and laid her panties on the exact spot I found them on. I even tightened the sheets on the bed, and fixed the pillows like they were before I had moved them. I walked out, went home, and thought about what I had done all day, only to replay it in my mind that same night as I masturbated.