Google has been renting textbooks in the US and a few other countries since August 2013, and now that short list includes South Korea.
According to Yonhap News Agency:
E-book readers can borrow a book via a download of the publication from Google Play, the app store created by the world's No. 1 search engine, Google Korea said in a statement.
The book is offered at about a third of the selling price for a 180-day rental, and the price varies depending on the period of rental that ranges from 24 hours to 360 days. Google plans to increase the range of publications for rental service in the future, by which it hopes to contribute to the e-book market in Korea, the company said.
The consumer/student rental ebook market is so small that I can't tell you for sure who Google is competing with in South Korea (the institutional, academic, and library market is a separate case). Google's retail competitors in South Korea include Amazon, Apple, Kobo, as well as local ebook retailers like Kyobo Books.
The demise of Coursesmart last year showed us that there wasn't much of a market for rented ebooks, but that hasn't stopped Google from incorporating it into their education platform, Google Play for Education, in January 2014.