Comment 3 for bug 32940

There are two workarounds necessary here:
first, if you don't choose a keyboard and language from the splash you are later presented with the correct menus to choose from (country, language and keyboard).
Later, if your keyboard settings in xorg.conf are "mixed" (I had pc105 and jp in there) you can correct this to jp106 (and jp), either manually or with dpkg-reconfigure xserver-xorg.

So even choosing a language and keyboard from the splash, one should still be presented with all the menus (just defaulting to the guessed values).
And then, for japanese keyboards, we should get rid of the "pc105" entry in xorg.conf (maybe this does not occur when selecting japanese as language?).