This is not the best Korean love story ever filmed (that may be "Il Mare") but it wasn't as unsatisfying to me as it was to some people. It takes the premise of someone going back into the past to save someone he loves and gives it a genuinely ingenious twist, which I won't reveal, except to say that if you see it coming you're a lot smarter than I am.
A young man named Sunwoo is bemused to find a single calla lily on his desk each morning when he goes to work, and occasionally he picks up the telephone only to hear piano music. Investigating, he discovers a nearby flower shop in which two young women work. One of them, Jihee, is especially beautiful, and Sunwoo finds himself falling in love with her.
Eventually he gets up the nerve to tell her how he feels -- but only on the phone. He arranges to meet her in the top-floor lounge of a hotel, only to arrive as she is killed by the man who is holding her hostage.
Stunned, he takes the elevator down and finds that he has been delivered into the past. Once he is over his shock, he realizes he has been given a chance to rescue Jihee. From this point on, nothing goes as the viewer would expect.
The film's narrative is a bit disjointed, although that may be partly the fault of the English subtitles, which aren't perfect. (They're not Hong Kong-terrible, either.) The leading actors are attractive, but only one of them -- the other young woman in the flower shop -- really came off the screen for me. And that's probably the movie's biggest problem, because we want to be fully invested emotionally in the characters. Still, all three of them are pretty and nice to look over the length of the film.
Overall, a pretty good movie -- one I can recommend especially to romantics. A lot of it happens around Christmas and there's lots of snow, so huddle up under a blanket with someone you love, or (at the very least) like quite a bit. You'll be better friends when it's over.