Always check your credit card statements, but I'm not sure how this has anything to do with Kobo. The article was pretty clear that it was about Rakuten.com, which serves as a marketplace for multiple vendors. Presumably they also use a separate payment system. Based upon the meager description, I suspect that someone found a way to scam Rakuten.com or that their security mechanisms failed. While it may affect Kobo, I somehow doubt it.