You might want to look into the immigration procedure here in Japan first. The people are great; almost all that I've met are fine with foreigners. But not so much the government and companies. You need a fair amount of patience to make it here (especially in the work place), unless you already have a contact. Good luck.
I was referring to residence, being able to live and work legally. Although I don't have any sources, I've heard of a few people who have become citizens. I don't believe it's impossible, just very difficult. Permanent residence on the other hand isn't rare at all.
