Japanese will have more incentive to buy BTC. Classifying as a financial product means the tax rate on BTC gains (or trading) goes to 20% instead of being the marginal income tax rate (43-55% if you earn >57k USD per year. Metaplanet will lose its tax arbitrage advantage over self custody BTC. Around 110 cryptos are also included, staking gains are taxed at the marginal rate.