This all started in biology class at school when covering reproduction.
I was 15 at the time and was in a biology class at school. Also in the class was this neighbor girl that lived three houses down the street from me. We had been covering reproduction at the time and had been studying about the female and male contribution to reproduction being the egg and the sperm. At our age, we were all very curious about what we were studying and learning.
I, my neighbor girl named Nancy and another girl from the class were at Nancy's house after school. We got to talking about what we were covering in the biology class. When the conversation got to the male contribution, Nancy brought up that they had a microscope and how fun it would be to see some sperm under it. So, the talk turned to where they could get a sample. Both girls then looked at me and ask if I had any ideas where they could get a sample all the while giggling. Nancy then went and came back with the box containing the microscope.
We got it out of the box and they again ask me again if I could give them a sample. I turned all red in the face but down in my pants I was feeling excited at how things were going and I started getting a boner. I then told them 'If you really want one I guess I can'. Nancy then reached into the box and took out a little jar and handed it to me. They were both giggling when I turned and headed to the bathroom. They were old enough to know about boy's jerking off and knew that was what I'd be doing to get them the sample.
I went into the bathroom, locked the door and proceeded to jerk myself off and shooting off into the bottle. When I had recovered, I headed back to them with the fresh sample. I handed the jar to Nancy and both girls were very curious at what they were seeing. It was there first time ever seeing semen and they looked at it giggling. Nancy then put a finger in it and felt it commenting how slimy it felt. We then put some on a slide and put it under the microscope. We all took turns looking at it with its live sperm swimming around in it.
After this, the girls got to talking about how I got it and started giggling again. Then Nancy brought up that we should do this again but next time watch me get them the sample. Both girls went to giggling about this and ask me what I thought about the idea. I told them I was game. To me, it would be a big thrill as I'd be showing my dick to a girl for the first time and it would be hard.
So, the next day at school, the girls came to me asking if we could do it after school. I said yes. They again went to giggling and I got a big boner just thinking about it. All the rest of the day at school I'd think about what we had planned and I'd get hard. It was a real battle trying to control this. As the end of school approached, it was a losing battle. I was so excited.
When school finally let out, the three of us took our bus, sat together and then walked the rest of the way to Nancy's house. The whole time I was fighting to conceal my boner. We went in and the girls quickly went and got the microscope box again. Nancy got out another sample jar and looked at me giggling and ask 'Are you ready'? I said 'Yes'. I started going to the bathroom when Nancy said 'Let's do it here. We're all alone'. I said OK. Nancy pulled out a chair in front of me and Charlotte, the other girl, joined her. Nancy had the jar in her hand. I asked them 'Are you'll ready'? I was so nervous but all excited.
I undid my belt and top button. My hands were shaking I was so excited at this. Here I was getting ready to show my hard dick to two girls and let the see me cum. I dropped my pants and then pulled down my shorts. I then stood there as the girls sat and looked at my hard dick. It was literally bouncing around from excitement. Then Charlotte ask 'Can I feel it'? I told her 'Yes, go ahead'. Both girls started touching it. There touch there was sending these charges all through my body.
I then put my hand around my dick and started to slowly stroke it. Both girls were all eyes. Then Nancy ask 'Want me to do it'? I told her 'Yes'. Nancy put her hand around it just like I had and started stroking it. Her hand on me like this and seeing me like this made my orgasm come on almost instantly. She no more than got to going good when the feeling started building in me real quick and I told Charlotte to get the jar ready. She held the jar under the head of my dick while setting right in front of me. I was so close to cumming that I couldn't do anything about the set up and I started shoot my cum. Of course, it shot right over the jar and ended up on Charlotte's blouse and skirt! She jumped up to get out of the way and the rest ended up in her chair. Both girls were shocked at how it shot out of my dick. I guess they were expecting to see it just pour out of my dick and into the jar. Needless to say, we didn't get any in the jar that day.
After this, I ended up going over to Nancy's house and we ended up doing mutual on each other quite often and became boyfriend-girlfriend. This went on through high school and we also ended up doing other things with each other as far as sex goes. She was my first for lots of things.