If japan goes into the mining business, it could also help to offset miner centralization which led to bitcoin unlimited having so much unfortunate support.
Russia entering the game could also have more positive effects in terms of increasing miner decentralization and nullifying china's influence on crypto.
I don't think japan will offset the miner centralization of china simply because the electricity rate there is very high compared to china. It's another thing if they use other kind of power beside electricity. On the other side,it's good to see bitcoin grow very well in Japan.
Answering the op, i think about 2 more exchange will launch in japan this year.