cool hand luke 22:36, Japan is a very racist (nationalist?) country. Any outsider is a threat and any outsider that can speak the language is an even bigger threat. Language is the advantage they have and once that is gone, they lose a lot of their control.
As for the "No Americans" signs, in some regards I don't blame them sometimes. There are some Americans that truly get out of hand because, well they're idiots and I wouldn't want them in my place
On the other hand, it hits a little nerve to be blatantly discriminated against and not be able to protest, so to speak, since in the US, that's exactly what would happen. It just doesn't work that way here. On a side note, a few of us have been allowed into several of these establishments when vouched for and were with a well-standing Japanese counterpart.
Don't misunderstand these 'ugly' statements that have been made about what goes on in Japan here in this thread. They are real and it is not "Asian bashing" to observe so. It is the part that goes with the "the good & the bad". Any level-headed person who can reasonably establish themselves within the culture and function can be witness. Much of this 'ugly' is seen right outside the base. It is so because there is like this bubble that encompasses businesses, people and their attitudes within the US base range. Get out past that, into areas where if you walk into a noodle shop, the entire place goes silent to turn and look at the gaijin who just walked in (lol), it is good. One still must act and talk appropriately, and they will still have reservations until proven otherwise.
Japan is a good country. But don't be disillusioned believing it is purely Wonderland.