http://bugs.winehq.org/show_bug.cgi?id=13829
--- Comment #7 from Michal Suchanek hramrach@centrum.cz 2009-04-23 07:29:54 --- Technically you can run
$ LC_ALL=ja_JP.UTF-8 LANG=ja_JP.UTF-8 wine testwin.exe [1]
and that should display a window with a few latin and a few kana characters.
This, however, does not test for Japanese fonts as such but for Japanese fonts properly linked with the system (or dialog or whatever) font.
[1]http://bugs.winehq.org/attachment.cgi?id=10369