As a foreigner, living in Japan is like being a guest at your friend's house. You'll be treated great, your friend and his family will be very courteous and polite to you, and you'll be able to do pretty much whatever you like around them. However, no matter how well you're liked or how much help you are, you can't truly become a member of your friend's family. There are some rooms of the house where they really wouldn't like you to be snooping around in -- the master bedroom closet, for example. It's not because they hate you, but just because the idea of your presence there is just plain weird and uncomfortable. You could be friends with the guy for 30 years, and that'd still be the case.
If you want to live in Japan, it's important that you're able to understand this and cope with it effectively. A lot of folks live in Tokyo for a few months and think "Pfft, what're they talking about!" -- and then it hits them when they're unguarded and it starts to make them terribly homesick.
As for black people -- well, you have to understand that racial caricatures were pretty common all across Asia well into the 80s simply because nobody told them that they were bad. There was a top-selling brand of toothpaste in China called "Darkie", complete with laughable engraving of a black guy in a top hat. They named it that because black people, in their eyes, all had really white teeth. This didn't go away until 1985, when the brand was bought by Colgate and they changed it to "Darlie" -- the Chinese name (which literally meant "Black Man" remains the same.