Hi there, I picked up a KT hoping to do the same thing in Canada.
Using a JP IP address via Tor, I managed create an account on rakuten.kobobooks.com. I can click on free books to add to a library, but didn't see any way of manually downloading them using the browser.
When I run the Kobo Desktop App, it knows I'm not in Japan and will only accept the regular kobo account.. so I can't figure out how to get the japanese account associated with the device. Setting the language in Kobo Desktop and on the KT to Japanese didn't change anything.
The "log out" function on the device is also a bit annoying, in that it resets the entire device, and reenables all the facebook garbage.
Using Calibre, I was able to setup a few japanese newspapers to download. I had to create a /fonts/ directory on the device, and copy over a few japanese fonts from windows, then set the font manually for it to view properly.
In contrast, my account with Amazon.co.jp will let me order physical books, ship to JP address, then have someone ship overseas. They don't care that I'm using a non-JP credit card. (We do have a JP card, but it doesn't appear to help in this case)