Apparently in Japan, there is a fairly new phenomenon called 'sex happening' clubs. The well-known US fetish queen Midori recently went to investigate Tokyo's fetish scene, and regarding these clubs, she reports:
...what the Japanese have are private, membership based sex clubs called "happening bars." These are similar to swingers clubs. I went to a couple of them and enjoyed the relaxed atmosphere, good facilities with serious sex furniture and friendly staff. Since so many homes and apartments in Japan are tiny, and not necessarily soundproof, these clubs provide couples with a comfortable play space away from home. Unlike a swingers club, I felt no expectations for people to engage sexually with others, but opportunities were available for those who desired it. Some of the staff would do demos or casual lessons for the members. Peer-to-peer instructions happened a great deal as well.
As I said, this is news to me. When I lived in Japan, there were the ubiquitous love hotels for private encounters, and hostess (as well as host) bars for drinking/socializing. However, I am not entirely surprised. If anyone has more info on these so-called sex-happening places, please feel free to comment.