To enable the Nokia N93 to display Japanese is relatively easy.
On a Central-European N93 you'll see the following files located in it:
NOSNRS60.ttf
NOSSBS60.ttf
NOTSBS60.ttf
S60ZDIGI.ttf
Upon reboot, the N93 will read the fonts on the microSD card and use them instead of the built-in fonts.
This should also work on other Series 60 version 3 phones, but haven't tested.