this forum is really alive, thanks for all your comments. My wife still has a Japanese Credit Card so the Sony Reader could be an option. On the other hand she really likes the Kobo Touch.
I hope to get it next week. For VPN btw I'm using PacketiX.NET (
http://www.techgravy.net/packetixnet-free-vpn-service/). Its free but slow. I was able to download a free ebook over the browser, but also I was able to get a free book in the App Market. Because of the VPN connection the whole PC appears to be in Japan. I hope, that when I connect my future Kobo it will sync the books.
I will let you know hopefully next week. Cheers