To use Japanese locales on a character-based terminal (TTY) you must use terminal settings to make line editing work correctly.
If your terminal is a CDE Terminal emulator (dtterm), use stty(1) with the argument -defeucw in any Japanese locale (ja, ja_JP.PCK, or ja_JP.UTF-8). For example, in the ja locale you would type:
% setenv LANG ja % stty defeucw
If your terminal is not a CDE Terminal emulator but the code set of your terminal is the same as that of the current locale, use stty(1) with the argument -defeucw.
If your terminal's code set doesn't match that of the current locale, use setterm(1) to enable code conversion. For example, if you are in the ja locale but your terminal requires PCK (Shift_JIS code), you would type:
% setenv LANG ja % setterm -x PCK
See the setterm(3CURSES) man page for details.