After basketball practice one day I went with a friend of mine over to her house. We both needed a shower badly, but she had a couple things to do when she got home so I went first. I had left all of my clean clothes in her room, so when I was done I just went back in my towel. Since her parents weren't home yet, a few minutes after she stripped naked and went for the bathroom. I laid there watching TV for a couple minutes before I decided to get dressed, but when I dropped my towel and started getting my clothes out, I started getting wet.
I needed to take care of it, so I got back on her bed and started rubbing myself. I laid there with my knees apart and the soles of my feet together (my favorite way to masturbate), rubbing my wetness all around and fingering myself hard. I guess I lost track of time, because when I was getting close the door opened and she walked in. When she saw me she started laughing, which made me start laughing too. I told her not to make me laugh because I was so close, so she got on her computer and I went back to fingering myself. It didn't take long, but I came hard and shook on her bed. When I was done, I saw that she was looking at some porn and touching herself, so I just laid there naked waiting for her to finish. After we were both done we just stayed naked until her parents came home.
Neither of us have a problem with masturbating or being naked around each other. One time I even had sex in front of her at a party, but catching each other doing it is still something that's funny.