When I was in eighth grade my next door neighbor Kathy was also a classmate. I got her a microscope for her birthday. In the past I had asked her several times if she'd like to see my penis and that I got an erection thinking of her. I could tell she was interested but told me her mother had caught her playing doctor with another neighbor when she was in the fourth grade and was afraid of being caught again.
We looked at all kinds of things under the microscope in her bedroom, which was on the second floor of her parents 100-year-old home. We had some privacy even though we had orders to leave the bedroom door open. Sometimes I would brush my hand over her breast, and she didn't complain.
We had often talked about sex. We asked each other questions concerning sex. I told her about ejaculating semen when I masturbated. At this time we hadn't actually done anything together so it surprised me when she got the idea to look at my sperm under the microscope.
I asked Kathy if she was sure and she said yes. So I dropped my pants right then. I was immediately erect and laid back on her bed. Kathy got a specimen bottle and I told her to keep it ready. So I was lying on her bed jerking off while she watched, very much amused. It didn't take more than 30 seconds and I was beyond the point of no return. I told Kathy to quickly hold the bottle at the tip as it was going to shoot. I came spurt after spurt, some in the bottle but most on her hand and me. Kathy was amazed and I was drained. We looked at the semen under her microscope and saw lot's of active sperm.
Kathy and I had many more experiences with masturbation, if there are requests for more I'll be happy to share them.