Okay, it was a nightmare for me to figure out how to properly configure this, so I figured I may be able to help other Linux users with configuring this. I almost got it working with IBus, but I could not get kana to output when the keyboard layout was set properly, so I switched to using Fcitx and now it's golden.

If you are one of the 0.00002% of people out there like myself who use kana input, this guide is for you.

For the record, I am running Manjaro Linux 64-bit. Manjaro is based on Arch Linux, so this should be useful for users on an Arch-based platform. This guide may help users on an alternate distro as well (Ubuntu, etc.), but some of steps may be slightly different and require a bit of extra research. Proceed with caution.

Initial Setup

Install the required packages

First, we need to grab some tools using our system package manager, pacman.

  • an Arch User Repository (AUR) installer. I am using yay, which you can install by running:
    sudo pacman -Syu yay
  • fcitx should already be on your Manjaro/Arch install by default, but if using another distro, or it simply is not there, install it with:
    sudo pacman -Syu fcitx
  • fcitx-mozc must be retrieved from the AUR, so to install it, run:
    yay fcitx-mozc
  • lastly, get the fcitx-configtool GUI by running:
    sudo pacman -Syu fcitx-configtool

Set the necessary system variables

Now we need to add some system variables in one of two places. Create/edit a file called ~/.xprofile.

export XMODIFIERS=@im=fcitx
export GTK_IM_MODULE=fcitx
export QT_IM_MODULE=fcitx

These worked fine for me in ~/.xprofile, but if it does not work for you, some users suggest putting these at the end of your ~/.bashrc file instead.

Before we are up and running we need to logout/restart (take your pick) to allow our system changes to take effect. Do one or the other and log in. Check your notification bar to see if fcitx is running, or if you're not sure, just run fcitx -d and it will either send you an error saying it's already running or it will start the fcitx daemon in the background. If this locks your terminal, hit Ctrl + C to get your terminal back. This does not kill the daemon for me, so I hope it does not kill it for you.

Now let's add and configure the mozc, our IME, inside of fcitx. Run fcitx-configtool in your terminal, and go to the Input Method tab. There you should see your current keyboard layout.

Click the + button and start typing 'mozc' into the Search Input Method bar. Select mozc and click OK.

Fcitx/Mozc configuration for kana input

Next find the applicaton icon for mozc (which looks like a keyboard) in your notification tray which should be in one of your panels if using XFCE. If you use a different desktop environment, you will have to do some google-fu because I won't be much help here. Point is, there should be a keyboard icon for fcitx somewhere.

Then go to Input Method > Mozc
Then go back into the fcitx menu and go to Mozc Tool > Configuration Tool and the Mozc settings dialog should come up.

Under the general tab, set Input Mode to Kana and close the dialog.

Now this was the big easy fix for me:

There are two buttons beside + and -. There is the preferences config button (icon looks like a few slider knobs) and the keyboard layout icon keyboard icon. Select Mozc in your input method list, and click the slider knob icon. There should be only one option on on both of them, a keyboard layout.
If you effectively set both of these to your actual device's keyboard layout, you will be able to type kana with the correct keys. My device orignally uses an English (US) layout, so I set both to English (US).

Last step is just to logout/restart and log back in and all your keys should be mapped correctly!

If this guide still left you confused, frustrated, and in need of more kana input help, check out the Arch Linux wiki pages on Fcitx and Mozc for further assistance. That's where I read up on most of this information.