IntroductionSince Kubuntu 9.10 there is a movement to replace skim  with ibus  that seems to be a better alternative. Unfortunately after my latest upgrade to Kubuntu 10.04 this movement caused my Japanese input to stop working.
To get Japanese working again using ibus was actually very easy and here Iexplain the steps to do it.
Uninstall SCIM/SKIM packagesFirst we uninstall all SCIM and SKIM related packages to avoid any kinds of conflicts with the new iBus system.
Install iBus required packages
Second we install the iBus packages needed to support different language input methods.
Configure the system to auto-select the input method.The im-switch utility is used to select input methods. For better results make sure you select auto.
- Japanese/Chinese/Korean/etc does not work in any applications. Make sure you have all scim/skim related packages uninstalled and all required ibus packages installed. Also make sure you ran the im-switch command (with sudo) and set ibus in auto mode.
- Japanese/Chinese/Korean/etc input work in KDE apps but no in GTK (Firefox, Chrome, Skype) apps! This happens if you do not have the ibus-gtk module installed or do not set the im-switch to auto.
- Japanese/Chinese/Korean/etc input work in GTK (Firefox, Chrome, Skype) apps but no in KDE apps! This happens if you do not have the ibus-qt4 module installed or do not set the im-switch to auto.
Resources http://www.scim-im.org scim/skim