There is not japanese translation yet.
I tried to write ja.po but I feel it is difficult to finish.
- Some messages are hard-coded we cannot translate with poedit.
- Japanese requires complete and high-quality translation, partial is not wanted.
To keep CHIRP's UI design and minimize the cost to translate, I suggest
- window titles
- status display (e.g.  Completed Getting memory 1000 (idle)
- easy English which is written in rig
- data query to other network services (RFinder etc)
- developer related function :-)
- serious error
But many Japanese will say "this is not translated" to this idea.
I attached ja.po to evaluate Japanese version of CHIRP.
I hope someone (or me?) will continue the work, otherwise abandon.