@AColobus what a hassle for you!!
I have a number of Kobo accounts, (none in Japan), but my device uses a dummy account - that is an account that I don't ever sync to Kobo desktop, and never buys a book.
I only ever side load Calibre cleaned epubs onto my device, and don't use kepubs (which would only get onto the device if I synced it).
As soon as I buy a book (and after I've downloaded it into Sony Reader for PC) I import it into Calibre, so I never have to worry about having access to that ebook again. (Of course I keep backups of Calibre).
If I should happen to buy a kepub only ebook then I open Kobo Desktop for PC and sign in with the account that bought the book (which isn't the account that's on my Glo). I then use obok to import that ebook into Calibre and side load it to my device whenever.
For info, Canuck in Japan and a couple of other members who frequent this section also live in Japan and use their home country account as their primary account from memory. But they'll give you their tips and tricks I'm sure.
