In Korea, there are several Adobe-DRM-supported ebook stores.
The lists are,
www.booktopia.com
www.mobibook.co.kr
www.nuutbook.com
www.book2.co.kr
www.piuri.com
As a Nuut3 user myself, I'm quite sure those links work.
However, you need to be fluent in reading Korean as the sites require registration.
If you have any ereader that supports adobe drmed books, you can have access to korean books from the sites mentioned above. Even my Sony Prs 650 can read books purchased from the sites.