This is a hilarious and completely over-the-top love story. There were points in the film I thought it might be way too offscale, even for me. But by then, I was completely invested in both the lead characters. And I'm certainly glad that I watched to the end.
The basic premise here is highly cultural. You'd never catch a Westerner doing any of the things that Kyun-Woo (Tae-Hyun Cha) does in this film. You'll have to just accept that Apparently, this story is based in a real-world romance. This is a great film mostly because of the power of the leads. One thing I remember from acting classes is being told that if your character is going to lie, make damn sure you are really lying. I have never seen an actor pull this off better or more completely than Jun Ji-hyun (The Girl).
Do yourself a favor and watch this to the end. You'll be glad you did.