I've been watching K-Dramas for about 5 years now, and I can confidently say that this drama is one of the best i've seen. Though it is lengthy and the story sometimes feels like a stand-still, It's all worth it the end. The chemistry is unreal, the childhood flashbacks give me chills every single time and the acting is phenomenal.
What is so amazing about this drama is the fresh way the story line progresses, It has very similar aspects we all know and love like the cute stuff that makes us hate being singe, but the intense horror/crime aspect that can be tied in effortlessly in the same scene makes it all so captivating.
To conclude- WATCH THIS DRAMA, you won't regret it!