Tatsuhiko,
Have you downloaded and installed the language pack?
http://kmeleon.sourceforge.net/files/kmeleon05lang.exe
That might help with the display issue.
As I understand it, language display from Mozilla works in the following method:
1) A charset detector tries to detect the language specified by the page and displays accordingly.
2) You can also specify a default language so that it will always use the specified language for display. This can be set in the user preferences file for K-Meleon.
3) You can specify the fonts used to display the language improving the likelyhood that the proper characters display. That preference can also be set in the user preferences file for K-Meleon.
To see how to change your preferences, see this:
http://kmeleon.sourceforge.net/docs/custompref.php
Here is the list of Mozilla preferences:
http://kmeleon.sourceforge.net/docs/mozpref.php
I'm working on a list of possible additions to the Preferences panel for future releases and language support is already on it.
Let me know if you need more help with this.
Andrew