I'm going to try and keep this review short and with only minor spoilers (so beware). Also, I suppose I should mention this is my first review ever.....O.O...Now I'm suddenly a tiny bit nervous. Anyway!....

Story:
From the very first episode, this drama had a special "air" about it. Usually, I don't find drama storylines to be unpredictable, but this one was a whirlwind of unpredictability! It was great! - However, I agree with the people who say the story went a little flat in the second half of the show; some parts felt like they fell off the good writing cliff, unfortunately. Also, there were some elements of the story that just didn't "click" for me, they didn't really make any sense and the progress of the storyline came to a halt. That was disappointing but not unforgivable.

Characters:
I liked all the characters and really felt for them. But I do have one bone to pick. I think the villains should have been given better, stronger motives than what was written. Ru Na, in particular, could have been an excellent villain if she had been given a better motive than just "I love my sister". I thought they were going to give her a different route than what she ended up taking. It made her appear one dimensional which was a shame.

Acting:
No complaints! I'm one of those viewers that doesn't understand the hate L got for his acting; I think he portrayed Dan really well!

Music:
BEAUTIFUL! This is one of the best soundtracks I've heard since Goblin.

Overall:
This drama turned out to be a lot more gorgeous than what I originally expected. It has a tragically beautiful feeling to it that will lure you in and keep you guessing. I highly recommend this drama if you haven't seen it yet!