Unless you are fluent in Japanese try to stay near city centers, the further you stray from the cities the more xenophobic people will be. They won't be mean to you but you can tell that most people that don't have experience with foreigners are VERY uncomfortable with people that aren't from their country. Luckily you will be somewhat feared, white people are often seen as intimidating in my experience. Also, ignore anyone telling you to try to sleep with Japanese girls, the Japanese people prefer elegance over ruggedness. They will take a good looking skinny man over someone who looks toughs and scary.