You can't read Japanese books on the Cloud Reader, or on the Kindle for PC App, even once you've managed to buy them. For some reason those programs don't support Japanese text.
You can only read your Japanese purchased books on certain devices, such as Kindle Paperwhite, Kindle Fire or Kindle App for Android. Older Kindles also don't support Japanese.
You can at least now read Japanese manga purchased from amazon.co.jp on the Cloud Read on the computer (I just checked), which is progress, as I have never been able to do that up until now. No luck with the actual Japanese books though. English books all seem to work fine, even if they were purchased from the .co.jp store.
You can only read your Japanese purchased books on certain devices, such as Kindle Paperwhite, Kindle Fire or Kindle App for Android. Older Kindles also don't support Japanese.
You can at least now read Japanese manga purchased from amazon.co.jp on the Cloud Read on the computer (I just checked), which is progress, as I have never been able to do that up until now. No luck with the actual Japanese books though. English books all seem to work fine, even if they were purchased from the .co.jp store.