I think it's Japan. If i'm right, I read some articles that tells Japan would be consider as the Bitcoin Capital in the world because their are really legalized and implementing btc in their country. In fact, other country are not yet recognize btc therefore most of their investors that interested to engage in bitcoin will do leave their country and go to Japan just to do investment. I think that the main reason why people still engaging and patronizing it, is just because of a huge of opportunity and benefits that the bitcoin can offer and give to them.