You don’t get local Japanese feed, which is the best way to randomly find new interesting things.

In general, even if you’re on Mastodon, Pleroma, or other fediverse instance, you can interact with Misskey.

The reason why Japanese content rarely be seen on Western fediverse is due to blocking. A lot of Western instance blocks misskey.io, oekakiskey, etc. Remind you that Misskey.io has the second biggest activities on fediverse. Basically incompatibility of rules. One allows R18+ drawn content, others are not.

There English Japanese-centric instance that federate with japanese instance normally and still federate with Western fediverse. Sakurajima.social (Mastodon) and Sakurajima.moe (Sharkey) would be a good candidate.

They can federate as intended.

The question is the community. Most of Sharkey instance are English or other European languages.