They certainly are the new leader of any advancement in utilizing bitcoin since they've been pretty positive about anything related to bitcoin so far. Companies issuing bitcoin bonds, regulations for safely trading cryptocurrencies and overall positive reception of bitcoin, Japan is a lovely example of a country seeing the good things about bitcoin.
it's definitely well received by the japanese; i was over in tokyo the other week and many of the department stores (excluding restaurants) had signs at checkout counters indicating that bitcoin payments were accepted there. I didn't happen to have access to my private keys at the time, so I unfortunately couldn't try it out myself, but it was pretty interesting to see.
after china and Korea Ban bitcoin exchange
Are you think Japan now bitcoin world leader ?
What do you mean by bitcoin world leader, in terms of what? because as far as I know China is the nation that have the most cryptocurrencies in their possession thinking the fact that they almost control the 70% of mining power in the whole world so logically they have the no.1 leader board when it comes to crypto holdings. Japan maybe the number one country when it comes to accepting Bitcoin as a legal tender as their government fully accept it nationwide.
just controlling volume doesn't mean anything, for all we know they could just be holding that bitcoin to prevent circulation and use. personally, i believe widespread use is much more indicative of being the forefront of bitcoin use in this case; the more use it sees, the more commonplace it becomes, and will eventually become general knowledge to the people. at that point, the people and the government will look the further the possibilities of use, and develop the technology further as they become more involved with bitcoin than any other nation.