Can you please provide a link to a Japanese online gambling site, run by a Japanese company? Gambling, not sports betting.

I also think you might hit a bump with your interpretation of the law there. It's like saying buying drugs and get them to Japan is legal as long as you use bitcoin. As Teramoto-san found out, it's not: http://www.ibtimes.co.uk/japan-makes-first-arrest-over-alleged-drug-trafficking-using-bitcoin-1447857