I plan to spend next two weeks in Tokyo, and most of the time I want to spend on seeing as much as possible of this city. This is why it is also very important to me to know if there are any dangerous suburbs in Japan, so that I know from which places to stay away.
Well, from my own experience, I can only advise you on what to avoid in Tokyo. I lived there for two years, and I can tell you that if you want to avoid troubles, you should stay away from the Kabukicho area. It is well known that it is one of the favorite areas for the members of Yakuza, which was a reason good enough for me not to wish to see that part of this city.