I went to Tokyo a couple of years ago. So I am sorry I can't remember all the details. I can't remember the exact stop, but it was on the Mita line (it may have been Sugamo), just outside the station was a street full of pink salons. I tried to walk into one, but the guy at the door looked at me, crossed his arms to form an 'X' and shook his head. I thought I was out of luck, but he pointed me to a place a couple of doors down. He followed me there and spoke to the doorman of the other place. The only thing I understood was 'gaijin'. This new guy then turned to me, and started speaking in broken english. The only thing I understood was 'covered'. I said OK and he let me in. He offered me tea and soon after a girl came in and gave me tea and did her business.
I may have been lucky that I ran into a doorman who was willing to steer me towards a place that is 'gaijin' friendly. If you are japanese, you definitely get preferential treatment, but I think that there is fun to be had in Tokyo even if you are not Japanese.