At a friends house
The backseat of my 1976 Mercury Capri. I was 17 and 6-0 tall; she was 17 and 5-10 tall. A very cramped missionary style. The next weekend we did it in the back hatchback with the second row seats folded down; she rode me in cowgirl. That was much better, and I lasted much longer (a minute, lol)
There were six of us together having a pash session. Two started to fuck. The guy I was with asked if I wanted to. I said yes - it was one of the most interesting few minutes of my life. We undressed and he then got into me. I had no idea of what to expect.
The other couple followed us and there were three couples all fucking on the floor almost touching. It was so interesting. We were talking to each other as we got fucked and after he came I agreed to swap and fuck with one of the other guys.
I had it twice the first time - two different boys - and loved it. We all talked about it afterwards for ages and it was amazing at what each one of us felt. I have never forgotten how much I enjoyed that day.
I relived it often after that. I couldn’t say no.
With hindsight it wasn’t the big deal many girls have but it was extremely interesting with us all discussing what each of us felt.
I enjoyed it both times and have done for 100’s of times since, if only I knew then what I know now.