Seems, changing LANG= value to ja_JP has no effect. Therefore, probably the culprit is the Gnome English UI package. Something is changed in IM relations, making UIM incapable of switching to MOZC, when switched to Japanese layout.
Tried installing ALL and EVERY uim & mozc package. The "conversion mode" underline appears under the symbols, when "hankaku-zenkaku" button is switched. But no hiraganam or kanji conversion happens; <space> just exits from "conversion mode", instead of offering conversion variants.
