@KaiTea:
From what I've heard from asking many Japanese students (colllege-aged), they're kind of scared of black people. Specifically, black men, I think. I ask them for some sort of rationalization and they can provide none. They're just not used to them being around. I'm not sure about black women; I had a black friend studying abroad in Tokyo and apparently she hated it, but whether that had to do anything with her race or not, I cannot say.
All I can say for certain is being black, you stand out more than a white gaijin. Also, in many urban areas, a large portion of the black population (I'm citing Amemura in Osaka for this) stand around all day dealing drugs. It's worth noting that that may affect the reputation of black foreigners in Japan.
Of course, if you're just going to visit, I doubt you'll encounter any of this. The chance of meeting someone who is racist or who is going to single you out is very low, and you will only encounter a serious probability of seeing them if you stay there for an extended period of time.
So that's the negative. You should know, though, that the positive far outweighs it
