I've found emacs for the Z supporting full UTF-8, even CJK characters in UTF-8 encodings properly, it also has the famous POBox input method support.
From this feed install:
and for help files
That's it. It'll read UTF-8 files in any lang including Japanese. If you have QPOBox installed, you can use it for input.
It has a console and X mode support, so you can also run it in X/Qt for a graphical mode.