Fantastic news, Japan was always know for highly rational people, it would be common to expect for such country to be one of first major retail adopters of Bitcoin. Bitcoin use is growing more and more, but what it still needs for large scale adoption is ease of use, currently to convert fiat into BTC is still quite complicated process over majority of exchenges which leaves out many less tech people out of it. It will get there but this still needs to be worked on and improved.