I don't think we should be surprise about this figure, Japan is a technology incline country and I expect them to have better understand of Crypto than most countries. The only fear I have is that they are not investing into wrong projects, there are alot of projects now that seems to be a scam
indeed, Japan is always been the leading country in term of inventing and adapting digital technologies so therefore when Bitcoin and crypto came in popularity it is not hard for Japanese to adapt and use crypto for their own advantage.
Japanese are very fond of involving latest technologies as it will qualifies them into the future of technology and while the world isn't adapting crypto, Japanese choose to adapt as early as possible.