When I was 13 and had begun masturbating, I would often go do it in our garage, which was back from our house. It was quiet and private there and I would push up against the corner of the workbench and do it.
One wonderful summer day, I was doing just that, with the side door cracked open so I could see if anyone was coming, when I saw my neighbor friend coming through the gate to find me... he was a year younger than me, and had always been very curious about sex and me.
On a couple of occasions we would be playing together when he would want us to 'play married', and would want me to lay on my back while he 'humped' me through our jeans.. saying that it felt good to rub against each other...
Both those occasions happened before I went through puberty, and although it did feel good to me too, nothing much else happened.
But this was a new day, I knew what would happen now and I wanted him to see me masturbating. I called to him as he entered our yard... he changed his direction and was headed for the garage...
I remember being filled with an excitement I had never experienced, knowing that I was not going to stop what I was doing, and that he would see me doing it!
He came through the side door and was immediately just laughing with excitement and saying only 'how big I was', as I just stayed there, pushed up against that bench, stroking myself in front of someone else for the first time in my life...
I know now that I am certainly not huge, but bigger than average.. I am circumcised and seven inches when erect. I assume that I was close to that at 13.
He was there just a minute when I heard my mom come out of the house, and saw through the cracked door that she was heading to the back yard to hang some wash.. she of course would pass right by the garage door, so I quickly tucked myself back in my pants.
My young neighbor immediately 'took control' grabbing me by the hand and saying 'lets go to my house, and you can do it some more'!
I silently obliged, and followed him to his house; he was moving fast and I knew he couldn't wait to get there!
His parents both worked and his sister wasn't home.. we were all to ourselves as he led me to his small bedroom and locked the door behind us.
He sat at his little desk in the corner and I sat on the bed across from him. He immediately asked me to 'do it some more'!
I unzipped and took my now softer penis out, and began to fondle myself again, to his obvious glee!
I was feeling embarrassed this time, and went to stop and put myself away, but he actually begged me not to.. saying 'please do it some more, please'
This time I pushed my pants and undies down and let them fall to my ankles, and took myself again in my hand.
As I slowly stroked myself, with him watching intently, giggling and so very excited to see me, I again became fully hard. Again, all he could say with expression of total amazement was how 'big' I was!
Sitting there stroking myself in front of him was the most exciting thing I had ever experienced. And, eventually it started to feel really good, and the thought of him seeing me ejaculate was even more exciting.
As the feelings rose within me, I asked him if he wanted to 'see me squirt' (knowing full well that he had no idea what I was talking about). He naively said 'you mean make it pee?'
I said 'no, it isn't pee, it's what makes babies'
I stood and walked, cock in hand, over to the desk where he sat, and said 'I'll show you', and pushed myself up against the corner of the desk, just inches from him.
I was rock hard now and throbbing, as I asked him 'do you want to do it', and let go of myself, leaving my cock standing alone, and bobbing.
He grabbed me and began to imitate my strokes.. it was the first hand other than my own to touch me there and it felt wonderful! Eventually I told him 'it's gonna squirt' as I felt the semen surge up my shaft and watched it release in a first shot that went over the desk and subsequent spurts that left a gooey trail across the wooden desktop.
He was amazed as he touched my cum.
After that, he would become obsessed with watching me masturbate and ejaculate. He would come over almost every day and ask me if I would do it again.
And again and again I would, every place we could and every chance we got. In our tree house, in his attic, in the bushes. It was the most sensual experiences I ever had.