Comment 5 for bug 1357313

Does not work for me as well. I had to switch to uim and uim-mozc , to get it to work I had to remove all ibus stuff and then had to mess with the settings so not exactly sure how I got it to work, was a bit of a pain.

Make sure to check your settings in Language support after you remove ibus everything, install the uim stuff, then make sure you logout and log back in. After that you have settings to set in:

Language support for the input method to uim
The uim-pref-gtk search for input method, you will see two options, for me it was the 2nd option, try them bot if need be, if the wizard comes up for the input settings, click cancel and try the other menu item.

From there click "Specify default IM"
Default input method set to Mozc
got to Toolbar (although I don't see a toolbar) chance check Enable menu-based input method switcher
Set effective coverage to whole desktop.

Logout / login after this you should be able to press shift+space and have Japanese 日本語できる