I found out about this place yesterday while talking to some Japanese coworkers before going home. We got into the subject after I told them about a hotel and sauna near my apartment that was apparently used as a hook up place for gay people.
So this spot in the picture above, which is the restroom at platform 13 of JR Ueno station, is supposedly a place where gay folks meet up and do each other favors. I looked it up online and this seems to be relatively well-known among the Japanese. I even found some info about it in English. According to my coworkers, the reason why this restroom in particular is being used for such “activities” is because it’s the farthest from the station offices, and hence isn’t visited very often by station staff. However, the authorities do know of what goes on in this public toilet, so the police are said to drop by randomly.
Very curious about it, I actually dropped by after work. Looked around, walked in, used the urinals, then left. A couple of other folks were in there taking a leak. The only thing I noticed that seemed out of the ordinary were a lot more signs than usual about how “disorderly conduct” will not be tolerated, and large stickers that say that the police frequently patrol the premises.