The goal is to make the system capable for Japanese input, while letting the base system remain English. For the Japanese input method, I had been using Anthy, but I will be using mozc, which is now better supported and presumably much better (it is).

First, set up locales and install im-config. In addition to my base English locale (en_US.UTF-8), install Japnese locales ja_JP.EUC-JP and ja_JP.UTF-8:

$ sudo aptitude install locales im-config
$ sudo dpkg-reconfigure locales

Set the default locale for the system to en_US.UTF-8.

Install some Japanese fonts:

$ sudo aptitude install ttf-kochi-mincho ttf-kochi-gothic ttf-sazanami-mincho

IBus

Install IBus-related packages and configure for KDE:

$ sudo aptitude install ibus ibus-mozc ibus-qt4 ibus-gtk ibus-gtk3 ibus-clutter
$ im-config
... choose IBus ...

Run the IBus setup program:

$ ibus-setup

If asked, start ibus-daemon. Log out of the KDE session, restart the X session, and log in again. Under the Input Method tab, add “Japanese – Mozc”. Configure IBus to my liking, such as making Ctrl + Space (as opposed to Shift + Space) trigger the Japanese input mode. The IBus icon also shows up in the system tray, from which various settings can be changed.

Mozc

Run

$ sudo aptitude install ibus-mozc mozc-utils-gui
$ /usr/lib/mozc/mozc_tool --mode=config_dialog

to configure Mozc to my liking.

Using Japanese in Emacs

Install ibus-el:

$ sudo aptitude install ibus-el

Within emacs, M-x ibus-mode will toggle IBus on and off. Very easy!