Actually, this makes perfect sense:
1- Rakuten is a back-end ebook player just like Kobo: http://www.engadget.com/2011/06/13/s...-book-service/
2- The japanese ebook market is stalled: http://publishingperspectives.com/20...ook-isolation/
Kobo had a global vision without global pockets, Rakuten has the money but not the reach.
And Indigo is betting on retail.