Hi khazum,
seems it is doable. I have attached pictures for your reference.
Please to see if this is what you need.
Also, I just use a common pages for Chinese, you might need to change the “Unicode Range” for Japanese version.
Also (again…), if you have the set of characters you want to use, you can define the file path and file wildcard to limit the offline cache size. there is no need to cache everything in your case I assume.
Hope this could be helpful to your project.