Notepad++ Japanese.

1. Installl npp.5.0.beta.bin as usual

2. Download Japanese language pack.

Notepad++ 4.0.2 用日本語ロケール

http://homepage3.nifty.com/georgei/extension/notepadpp_jpl_v09.zip

3. Extract nativeLang.xml to npp.5.0.beta.bin\

4. Restart notepad++

5. From menu: Format -> UTF-8