Watching my gf
I dated this 31 year old gal for about a year. She was a CPA and normal in every respect that I knew. She had a 12 year old son from a relationship that didn't work. I always thought the kid was a bit introverted but never really got to know him.
I went over to her apartment and we were cooking dinner and her son came over and asked Cindy if they could play the game. She hesitated for a moment and then said, this is just an innocent game we play. She sat on the sofa across from the kitchen and her son got on her knee and started riding her knee. She didn't do much but sit there. After 30 seconds the tempo increased and I could tell the little boy was going to ejaculate or dry ejaculate or something. After about 90 seconds it was over and she said go watch some tv while i finish cooking dinner.
We only dated about another 3 months after that, but I found it unusual and somehow a little bit arousing.