With the following Japanese IME(input method engine) fcitx-kkc you can input Japanese on your mobile device same like your computer.

To enter Japanese Kana or Kanji, default Users will use Google “mozc” as input method. But there are tracking free method available. It's called KKC or “Kana Kanji”. It does nothing more than convert the entered kana into kanji and it uses some dictionaries for that. It is very powerful and fast too. The current installation of default IME for Japanese is fcitx-kkc, which can be used on your computer also.

Make sure you have installed Japanese fonts. This fonts are needed to write and read Japanese contents on your mobile device.

sudo apt install fonts-noto-cjk

The following sequence must be observed during installation. You can do this in your “King's Cross” or by SSH.

sudo apt install fcitx-kkc

(Thereby a lot of further dependent data is installed. In total about 130MB.) Perform a reboot. This will prepare the keyboards for “Fcitx”, this cannot be done manually, so a reboot is inevitable.

After the restart 2 new icons of “Fcitx” are integrated, but these should not be started from the mobile device directly. Instead we use the command prompt via “King's Cross” (do not use SSH, this will not work).

fcitx-configtool

A window opens in which a keyboard is already included. This keyboard should not be deleted! Using the + sign to add another keyboard. A list with a large number of keyboard layouts appears, which we ignore. The checkbox “Only Show Current Language” must be removed. In the search you enter “kkc” and the keyboard “Kana Kanji” appears. Select it and click on “OK”. You come back to the list and now 2 keyboards are shown.

Now to activate the layout for the Japanese language. In the still opened window there are further tabs. There you click on “Global Config”. In this tab there is a button called “Trigger Input Method” and currently the default is “Ctrl+Space”. But “Ctrl+Space” is not comfortably to use on your mobile device, therefore let's change to another trigger like “Ctrl+Lalt”. For this we click the button “Crtl” and hold it pressed, additionally we press the left “Alt” key. Now release both keys. The button should have changed to “Ctrl+Lalt”.

The X on the window to closes it and we return to King's Cross. Now the Japanese input can be tested directly via an external keyboard or via the virtual keyboard.

There 2 ways

For a mechanical keyboard:

To activate the Japanese input, simply hold down Ctrl and press the Alt key. The message “Kana Kanji” appears briefly, so we know that the Japanese keyboard is active.

With a virtual keyboard:

The Terminal Keyboard should be used to activate it. First press the “Ctrl” key and then the “Alt” key.

If you enter a full Japanese word, only the Kana will be displayed. If you press the space bar, the word changes to kanji, and if necessary a list with a selection opens. If you press Ctrl and Alt again, the Japanese keyboard is switched off and you can use the usual Latin letters.