This is a continuation of my previous post here.
The only time I ever saw anyone else masturbate as a kid was once during the summer after the eighth grade. I'd been in puberty for about seven to eight months and I think I'd graduated from blanket humping to the fist. My best friend for maybe the past couple of months was a seventh grader named Jim. We had become constant companions but since my parents didn't exactly approve of his parents we never spent the night at either house. We played in the woods, built forts, did endless science experiments but oddly never ever talked about anything sexual.
One morning in early summer I went over to Jim's house as usual and since his parents worked shifts and often had to sleep in the day, I went around to his bedroom window rather than knocking on the door. When I looked in his window I saw him lying face down on the bottom bunk of his bed with both hands under himself about at dick level. His butt was working up and down as he thust into his hands or the blanket underneath him. No, he wasn't nude. He had on a shirt and jeans and since he was face down, I don't know if his penis was out or not.
I watched for a few seconds as the realization that my best friend was humping just like I did. I was embarassed that I was spying on him and had caught him in the act and I guess figured he'd be mad if he knew so I backed away and went round and knocked on the door.
A little while later Jim came to the door and I'm not sure what sort of stuff we did that day but I never told him that I'd seen him humping or asked him about it. I sometimes wonder what would have happened if I had.