Hangul-Hanja conversion is maintained by Hanja Tool, which manages two system files:
In the ko locale, the /usr/lib/mle/ko/syshjd file is system-wide and read-only.
In the ko.UTF-8 locale, the /usr/lib/mle/ko.UTF-8/syshjd file is system-wide and read-only.
In the ko and ko.UTF-8 locales, the $HOME/.usrhjd file can be manipulated by the user.