Maybe this will help:
Hikikomori - Wikipedia, the free encyclopedia
I think what RobinMask is asking for is quite a reasonable thing to ask for-- I've heard of people wih "asperger's" who seem to grow out of it. To me that suggests less of a disease and more of a basic social behavioral problem which can be fixed with a little experience. There are also people who obviously have a disease, though, too.
Judging by the topic's title, is it safe to say you have some of the traits of "hikikomori"? I think that while "hikikomori" can be sometimes linked to things like asperger's, it is often a lifestyle choice that some people make. I've heard people talking about it before, but I've never really met anyone who was like that. I can assume, though, that it would be hard to cope with something like that while in Japan. By nature a condition like that would kind of stop one's ability to look for support when things get bad. Foreign people in Japan often hang out with each other as it can be hard to find Japanese friends with a lack of language ability. Also if it's bad enough to prevent you from working/going to school then I think you wouldn't be able to live in Japan as that seems to be the top criteria for being able to live in Japan.
For visiting Japan I think it would be quite stressful going to a place like Tokyo or any other big city for that matter. There are so many people that it can be overwhelming for anyone!