This happened when I was 17 in the 60's. Things were different then, I had been going out with a girl for about 2 months but we hadn't done much more than than some heavy kissing i.e. tongue to tongue but this night we were watching some crap Elvis film at the pictures and we started to kiss and I soon got my usual hardon but this time she actually started to rub it through my trousers which was the most amazing feeling I've ever had because up till then I was the only person to have touched my cock.
She kept rubbing it and kissing me and I shot my load in my pants.I was very embarrassed but she just laughed and said one of her friends had told her that she had done this with her boyfriend and she wanted to see if it would happen with me.
I felt better then but I had a real big stain on my trousers.She asked me if I could do it again and I said bravely only if you stroke it. So to my surprise she said get it out which I quickly did and covered myself with my coat.
She started to stroke and kiss me and sure enough I was rock hard again (oh how I miss those days of the second cumming!!!).
My cock was already wet with my own cum and I was ready to shoot again and she whispered let me see you and when I was about ready I told her and she lifted my coat and watched me cum all over her hand and again my poor trousers. She giggled and said she couldn't wait to tell her friends (neither could I).
When we left I had to walk with my coat held in front of me to hide the massive stain.
When I got home I had to hide my trousers so my mother wouldn't see them and I was so horny I had to jerk off agian.
I went out with her for over 2 years and we learned an lot about sex from each other including full intercourse.
Oh how I miss those innocent and exciting days.