This was a true story that happened in Southern California back in the 1970s.
I played percussion for my school orchestra and band in High School and took private lessons as well. My teacher was putting on a concert for some of the local schools and asked me to join the percussion ensemble group he formed. There were six of us plus my teacher.
The rehearsal was about an hour from my house and my parents dropped me off. I was getting a ride back with one of the older players that lived closer to me.
One of the other players, Chad, who was also in high school lived near the rehearsal hall, and during a break we all headed over to his house. It turned out he had a swimming pool. Some of the guys had brought swim suits and Chad lent me an extra one he had, as we were both about the same size.
When it came time to get into my suit, one of the older college guys, Brian, joined me in the pool changing room. I was small for my age. I have blond hair and blue eyes, was maybe 5'6", around 115+ pounds and had a slim build. I certainly would have fit the description of a "twink", had that term existed back then. I was taking my clothes off, and as I slipped my underwear off and reached for the swim trunks, I saw Brian's reflection in the changing room mirror. He was standing, still fully clothed, behind me. He said something like, "nice package". Maybe he was expecting me to be less developed because of my smaller youthful appearance, even though I was 18. In any event, I was a little unsure what to think of his comment and just stood there.
He told me what a nice body I had and said I had been running around all morning and need to just relax some. Brian turned on the faucet in front of us and ran some warm water. He reach around and lathered his hands with the hand soap and warm water. I just continued standing there, like a deer in the headlights. Then, standing behind me he reached around with both hands and began to gently fondle my balls and cock with his soapy hands.
My penis quickly began to harden as I watched fixated, on my reflection in the mirror. Soon my cock was pointed straight up. Again he made some comment that made me think he was surprised at the size of my erection (which was probably around 6" when I was this age). Looking at the mirror I could see myself at full attention and watched Brian fondle my now soapy smooth sac in one hand and run the other over the length of my hard shaft.
He moved one hand up to my smooth chest and pulled me back slightly, until I was leaning back against his body for support. He held me close to him as his "free" hand wandered between my abs and chest. He kept up a slow steady jerk of my cock, "polishing" the knob and sliding down the length of my shaft again. Of course, it felt great, and I could feel the tip of my cock tingle with every stroke.
"That's right, lean back and let me help you relax and just enjoy the feeling," Brian whispered into my ear.
"Just let that tension cum out, don't hold back."
It didn't take long before I could feel myself on the verge of Cumming. My whole body stiffened as Brian continued jerk me off. Soon I ejaculated and cum shot out of my cock and into the sink and counter in front of me. Brian rinsed his hands off and toweled me off.
I never said a word, still too shocked by the whole experience. I slipped into my bathing suit, went out the door and dived into the pool.