Many many places are Japanese only and run by Yakuza so it is almost impossible to get in unless you a brought in by a local. There is a language barrier also. There are foreigner (gajin ) friendly places, but the sex workers are mostly Chinese, Korean or Filipinos. Japan is a misogynistic place with many sex starved women who will fuck foreigners for free, these women are often unable to travel out of Japan for that reason or have already vacationed out of Japan and now crave foreign dick. These woman can be found in Tokyo on online dating sites very easily for discrete free hook ups.