The update which enables Japanese language support is now live. Please do not forget that you can change the language of the game in the Language tab of the Properties: right-click the game in the Library section of the Steam client and select Properties. In the Language tab choose the language.
Please be aware that different language versions of the game do not share the save files, as well we do not guarantee compatibility of the save files among the versions of the game, because may lead to unexpected issues. Therefore we strongly advise to avoid performing such actions.
Added Japanese language support
Build and release context
Steam update times within 24 hours of this post. Matching dates do not confirm which build it describes.
Build 3977352 · public branch
Steam updated · First observed