Looks like there's currently a new big migration of Japanese users/artists to Mastodon.
I don't know why, I read that Twitter banned some Japanese accounts (reason is unclear).
Currently "pawoo", "mstdn.jp" and "マストドン" on Twitter returns a massive list of results. People don't really know where to go and make accounts on both.
The main issues are of course that both services are blocked by many instances instead of being muted. And that they're running Mastodon 3.x, which is an old unmaintained version ?