If you can’t find anything, you’ll need to change the Charset to “Shift_JIS” and translate the English into Japanese. This is what I have to do and it works perfectly. If you know PHP programming you can create a language switcher and language file that has English and Japanese. Then the user can simply switch between the two. I prefer the translations myself because I can keep the admin area in English while the front end is in Japanese. I also prefer coding in Shift-JIS because that is what Japanese people use. Anything else and it becomes difficult merge with other solutions as most Japanese software is in Shift-JIS.
@jimatwood,
Looks like you might be able to help me with my issue, based on how you responded to this post.
I want to do exactly what you did. Help? 🙂
http://wordpress.org/support/topic/285010?replies=3
YAK supports Japanese language by the way. At least there’s a translation (po/mo) which may be a little out of date, but easy to update if needed.