[kumaryu]

Interesting...

The main technical challenges facing Kobo in getting EPUB format ready for the Japanese market would be the following features currently unsupported by the format.

Vertical layouts
Line breaks
Ruby characters

I would imagine they're not insurmountable but the larger issue would be whether they would be accepted as a standard and whether they can accumulate enough content to make the format and their offering viable as a competitor to Amazon/Kindle.

The quickest way to achieve this would be to provide support for XMDF, the defacto standard in JP on Kobo devices. This is the format in which much of the book content on Rakuten's own site is provided.

In a market where a large propotion of publishers' revenues come from graphic novel-type formats and the line between traditional text and graphic novel is not as clear as in other markets, having a viable format for text is not enough o its own.