Japan is one of the leading Cryptocurrency Hubs of the world and there is no doubt in that. That being said Cryptocurrency Mining was not very active in Japan considering their cheap Electricity costs.
But lately, things are turning in Japan as more and more People's are starting to Mine Cryptocurrencies in Japan taking advantage of the low Power cost. Although it is very evident that officials will be cracking down on such Miners and would ask for Premium rates but that seems to be further down the Road.
The position of Japan on cryptocurrencies is quickly being solidified especially after the legalization of Bitcoin as a payment method and its lenient regulatory environment. Whether or not any of this will benefit the industry as a whole is a different matter altogether and we will be looking forward to that.