I read the linked story, and it reminded me of my own experience with another younger friend.
Alan at 13 was two years younger than I, and hung around with our older group sometimes making a peat of himself. I never gave him a thought as far as anything sexual was concerned, but was aware that he must have progressed into puberty judging by his deep voice. Our parents were members of the same club which had sponsored a series of lectures which they felt would benefit their kids, so it happened that he and I and our parents were attending one of these lectures which I found very boring. I got permission to leave, and went outside where I expected to spend the hour or so remaining of the boring talk by myself. A few minutes later Alan appeared saying that he too couldn't take the lecture ans suggested that we walk around the golf course to see if any of the other kids we knew might be around. I thought this was a bit odd in that it was dark and all of the kids of either of our ages were probably home, but we began walking. Alan steered the conversation around to girls, sex, and masturbation, and I got a big erection. He noticed that my pants were tented up, and asked me to take my dick out so he could see it. That surprised me, but there was a peculiar sound to his voice which I found irristable. So I pulled my six inch hard dick out for him to see. I felt really captivated by his voice wondering why I was doing this. While I was caught up in this reverie, I felt him feel my rigid penis, and looked down to see what he was doing. He had one hand on my dick and the other on his now exposed penis.
I asked him to stop in that I was afraid someone would see us, but felt unable to just end our encounter. He suggested that we go sit on a nearby bench which he thought would conceal us from being seen, so we did. When we got there, our dicks were still out, and he began to comment somewhat like this,
What a big one you have. You must jerk off a lot for it to be so big. How often do you do it?
Amazimgly, I replied that I did it two and sometimes three times a day, and asked him,
How often do you do it?
About the same as you, and I just started to squirt. Let's do it now.
So we began to jerk off with me at least feeling afraid of being caught. He seemed entirely concentrated on his penis which was about five inches long and rather thin. He kept commenting that mine was the biggest one he'd ever seen which got me really steamed up. When I came, the first rope went about two feet and the other five of so lesser distances with the orgasm ending with the usual oozing.
What a load, exclaimed Alan, and began to come himself.
His eruption was much less than mine, and the come was clear rather than milky to be expected from a boy of 13. I immediately felt ashamed that I had done this in a public place with a boy two years younger than I, but Alan's reaction was exurburant. He said that was the best orgasm he'd ever had, and begged me to come to his house the next day so we could do it again. I agreed.