So many 'firsts' for me when this happened.
I was 17 at the time and in high school. I had a steady girlfriend that went to a different school. She too was 17. It was on a Saturday and she was home by herself that day. I went over to see her and we ended up in her room and then in her bed. We were into some heavy 'making out' and The way things were going, it looked like we were going to actually have sex for the first time. My girlfriend was the one who started things going when she put her hand over my hard cock and started feeling it through my pants. I had never had a girl touch me there before. This was a first.
When she did this, I figured it would be OK if I also touched her 'down there'. I then ran my hand up under her skirt. I ran it up her leg. I had never felt a girl there before and did it ever feel good. I then went all the way up and started running my fingers over her pussy through her panties. She was very warm and wet there. I then went back to feeling her legs again. About this time, she raised her hand up and stuck it down the front of my pants wanting to feel my cock. She wrapped her hand around it and started running her hand up and down on the shaft. I then reached down and undid my pants and pushed them down. Another first happened then as she looked down at my cock. No girl had ever seen it before. She again wrapped her hand around it and started going up and down it again. I went back to feeling her up under her skirt.
I was so aroused and excited at this that I couldn't help it. As an old joke used to say, I was 'young and full of cum' and did I ever let her have it. I literally exploded and shot cum all over her. It got on her exposed legs, her skirt and some on her panties. I had received my first hand job from a girl and had a girl see me shoot off. She was such a mess that we had to stop, get up and go clean up.
After getting cleaned, she decited that we better not go back into her bedroom because her mother was expected before long. That other 'first' didn't happen for another three weeks. All I can tell you was it was sure good too just like her hand job. Believe me, this was only the first of many hand jobs I got from her.