This happened in 1972 in highschool.
In highschool, I was on the track team, running hurdles and sprints. A girl (I will call her Nancy) was also on the team and ran with me daily for practice. This one time, during a bus trip from a long meet, Nancy sat by me on the bus and we talked about the meet and stuff.
Suddenly without warning, Nancy mentioned that she noticed I was limping coming onto the bus, and questioned if my leg was hurting from running. At that point she began to massage my left thigh, unsuspecting of the other team members on the bus. I quickly took out my sweat shirt and used it as a pillow, as I leaned back and enjoyed the massage from Nancy.
I was dozing off when I felt her hand move up to my ever growing cock, as she cautiously unzipped my now tight jeans. She continued until she pulled out my swollen, eight and a half inch cock and held it in her hand. Hidden now by her sweat shirt, Nancy pumped my cock real hard, and suddenly, after a minute or two I couldn't take the feeling any longer and exploded a load of hot cum onto her fingers and the floor of the bus.
She quickly cleaned up the mess with her sweatshirt and continued talking like nothing ever happened.
A bus ride I will never forget.