The same director, the great Chan-wook Park, did this film before his Vengance trilogy. It was extremely big in Korea and is considered one of his best films. BTW, he usually uses many of the same actors in all of his films, so you'll see a few in this flick from Oldboy and the Sympathy films:
And I still stand by my recommendation of The Host. It's a monster movie for sure (and not really scary, but that isn't the point), but it's more about the eco-message and certain aspects of Korean politics, and the performances are across the board excellent (the female lead was in Lady Vengeance, J.S.A. and the male lead, Kang-ho Song, was in Mr. Vengeance and J.S.A.)