I am going to index wikis belonging to category:Japan or category:Japanese which use MediaWiki.

I may exclude wikis that are more or less private home page rather than community home page, such as wiki with only one registered user.

User:Nightingale/work in progress

Free wiki hosting

list: Category:Wiki farm

Wikia, Wikispaces, @wiki, Seesaa Wiki (previously known as Livedoor Wiki), CentralDesktop, WikiHouse