Sometimes it does not matter how many sex adventures you have, a particular episode stand out in your mind.
I have several but the most erotic but hardly sexual in the physical sense I was at a football match and in the standing area where it was terraced and meant the person in front was lower than the person behind. In my case I was in front and I had a couple behind me with the girl behind me but at one side. This put her groin at the same height of my upper arm and shoulder which I did not noticed until she started moving and cheering the action on the field. I noticed that her pussy was actually rubbing against me and I dismissed it as just coincidence, however as the game progressed her pressure on my shoulder incresed and I assisted by slightly turning my shoulder and fitted it so it was more direct between he upper thighs. This is how we watched most of the game with her humping my shoulder at any opportunity - which I was more that happy to do. I never saw her face but I certainly remember the encounter.
The second similar encounter was when I was getting a Haircut and I was in a tourist town and the girl doing my cut wore tight shorts a tank top - nice looking without being stunning. When she swung around me to cut my side hair her pubice area hit my elbow and I thought it was an accident but from then on everytime she would move either side she would rub agaist me. I tested it by pushing my elbow futher away from my body and she still continued very erotic.