This is how to get Japanese Fonts working in OpenELEC tested on version 5.0.0
Download a Unicode Font of your choice I usually use Arial Unicode or Sazanami Mincho and have put copies of these on my USB stick as sometimes they are hard to download from the INET
Add it to or create the folder /storage/.kodi/media/Fonts it is a bit tricky as OpenELEC does not let you add it to that folder using the network share so i usually add it to /storage and then move it to the correct location using SSH
Reboot for good luck and then navigate to System >> Video >> Subtitles and select your newly added font from Font to use for subtitles also required now is setting the Character set to Japaneses (Shift-JIS)
I also like to edit the subtitle offset amount as sometimes subtitles are 60 seconds or more out of sync do to commercials etc this can be done by adding a file called advancedsettings.xml to /storage/.kodi/userdata
<advancedsettings> <video> <subsdelayrange>60</subsdelayrange> <!-- Delay range for subtitles, in <audiodelayrange>60</audiodelayrange> <!-- Delay range for audio/video </video> </advancedsettings>