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/WorkInProgress
- Free wiki hosting
list: Category:WikiFarm
Wikia, Wikispaces, @wiki, Livedoor Wiki, CentralDesktop, WikiHouse