This occurred with a 10-year-old boy when I was 13. I had been masturbating for only a year and did it a little too much on a daily basis (4-5 times).
One day my sister's friend Eric, from across the street, came over and we started to play video games. Eventually Eric ended up sitting in my lap as he played and I was the 'restraints' like on a roller coaster. Since he was sitting on my dick I became rather horny. Eventually as time went by the 'restraints' got lower and lower until they were over his dick. I then began to move my hands a very little bit over the area. I did not feel his erection but I am sure that he felt mine. After a while he went home and I orgasmed several times to him and wild fantasies.
Over the next few months Eric continued to sit on my lap when we play video game and I continued to feel his dick. My sister seemed oblivious to what we were doing. One time I actually felt his erection but he immediately got off of me after that. I decided to stop the whole business. However Eric continued to sit on my lap and I couldn't help myself.
Sometimes when we were alone I would reach my hands down my pants and masturbate hoping that he would ask what I was doing so I could live out one of my fantasies. This did not work, but Eric did sometimes sit in such a way that I could see up his shorts and look at the edges of his white briefs.
The real story starts where he once pulled down his pants for a moment in order to tuck in his shirt. I then realized that he was willing to go a little further. The next time we did the 'restraints' one of my hands went down the back of his shorts and felt he elastic band of his underwear. He didn't mind so I felt okay in doing what I had always wanted.
When we were next alone in my bedroom (my sister had left for dancing and only my dad, Eric and I were home and my dad was outside) I reached my hands down my pants and began masturbating as Eric sat on my bed and averted his eyes while engaging me in light conversation about a picture on my wall. He had just gotten home from a baseball game and still had all of his stuff on although it was a bit dirty. My heart was beating very loudly as I got up and asked if he minded if I changed into my baseball stuff.
He said sure and got up to leave but I said it was okay if he stayed. I then proceeded to take off my socks, shirt and pants until I was only in my black briefs that were several sizes too small and extremely tight on my dick. I then made a false show of looking through my drawers as Eric probably watched me from the bed. I then turned and asked him if I could borrow his athletic cup (a thing that protects a guy's balls during sports), as I had apparently lost mine.
Eric said that it might be small but I insisted that I really needed one. He then got up to leave and I asked where he was going. He said he was going to the bathroom to take it off. I said that he could be open with me, after all I was standing in front of him clad in only my underwear. He seemed to relent and then to my surprise started to take off his socks and shirt, as well as his baseball pants. I could see that he had an erection. He wore his cup under his underwear and hesitated before sliding off his own briefs and then quickly followed by his athletic cup. He handed it to me and I took it.
I then slid off my own underwear and asked Eric what he thought of my dick. He said that is was very big and that he thought I was supposed to have hair there like his dad. I sat down on the bed and squeezed my dick with my hand before rapidly pumping it. I was so horny that semen shot out in only seconds and landed on his belly before dripping down to his pubic region. Eric then took a hold of his dick too and started pumping it. We masturbated ourselves and then did it to each other until my dick was sore from orgasming. He then got dressed and left, saying that he would very much like to do so again. He left his cup there and I wore it quite a bit.
Over the next 3 years Eric and I became good friends both mentally and physically. We had a weekly masturbating session at his house on Sunday when he was home alone. I even took pictures and videos of us doing this but always felt guilty and deleted them shortly afterward. What prompted me to write this was how this weekend I slept over at Eric's house and we had a splendid time. I will say that things got a little out of control. I now own a girl's thong and a condom.