I was in Japan a few months ago and I took the opportunity to visit a gay sauna.
When I was in there, I played with a Japanese man, aged about 25-30, fit body, cock about 5.5" long. We were lying on a mattress covered platform with quite a few other men of all ages and sizes.
I cannot speak Japanese, but fortunately, in a place like that, words are seldom used. In the full view of a handful of spectators, I started to work on him. Having sucked and licked him all over while he was on his back, I turned to lie on my back, waiting for him to reciprocate. Instead, he very smoothly and quickly enveloped his ass around my throbbing cock without so much as a bye your leave, and started bouncing on me. It was indeed an interesting and rather erotic sight to see his hard cock swing rhythmically with his every rise and fall. All the time, his hands were on the mattress or holding on to me so as to keep his balance.
It did not take long for him to climax, purely from stimulating his prostate using my penis. It was a glorious hands free orgasm, with him shooting all over my body. He then dismounted and very politely kindly wiped me clean. He did not help me to an ejaculation though. He was gone before I could ask for one. No, the spectators did not come to my aid; they too disappeared once the act was over.
That was the first time I was used to give a man a hands free orgasm.