Hi,

I just make Japanese language files for 4.1.2.

[url=http://foken.tk/wp-content/uploads/2012/01/ja_JP412.zip]Japanese 4.1.2[/url]

However, I do not use this current version. I use 4.0.5 at [url=http://foken.co.cc/]here[/url], and there is Japanese 4.0.5.
If someone have an interest with Japanese, please try it. If you find out miss-translation and have any request to change words, please let me know.