I am one of the thousands (ok, maybe hundreds of thousands) outside South Korea who diligently follows Korean Dramas (ie KDramas).
I first noticed Yoo Ah In in Sungkyunkwan Scandal where he played the role of justice-seeking rebel from a noble family. Not a lead role, but (hooboy) he commands on screen.
Then came along Secret Love Affair aired in Spring of 2014 (next week is the final run of this masterpiece). He plays the role of a 20 year-old piano prodigy who finds a soul mate and love in a 40 year-old Director of an Arts Foundation.