This will likely cause a massive tax evasion in the future. I don't mean anything outright illegal but rather something more like the "loopholes" people are discussing here. For example, you can become a tax resident of a country which has a soft tax regime in respect to cryptocurrencies (countries like Italy or Denmark) and officially pay (or not pay) your Bitcoin capital gains taxes there, thus avoiding paying the same taxes in Japan. Though I don't know if Japan has double-tax agreements with these countries.
Of course! And can you really blame people for doing it? If you had a friend that agreed to help you move things around and you threw him a 20kg bag, he'd most likely take it and come back for another one. If the bag was 40kg he'd complain about it being heavy but still keep going. If you asked him to carry 60 kg he'd be like hell no! I don't want to hurt myself! Taxes are a burden that should be made as light and easy to carry, so that people won't have the reason to complain and avoid them. Japan is overdoing it same as those countries that are imposing extremely high taxes on the rich, like France.