Hi there,
I've been doing work in Japan for some time now and although I would probably have my URL's in Japanese I found that if I hagoo sound meter data, correct charset for that language and good links from Japanese domains when the content of my pages are served pretty well. See example here - http://www.instantatlas.com/whatisinstantAtlas_JP.html
I would say that most traffic from the above page actually comes from Yahoo Japan than say Google Japan (it does come but not in the same volume). I have a Chinese equivalent and traffic to this landing page comes from Baidu. I would like to point out that for both pages they will drive Japanese, Chinese and English queries from these countries.
We are about to embark on an overhaul of this page to include easier navigation, structured data etc.
Happy to share outcomes on these change over the coming weeks if it helps.
Best
David