I should mention that this is one of my favorite genres. For lack of a name I'll just call it Suspense With A Supernatural Twist. I watch every one of these that I can get my hands on and they almost always delight me. Which is to say I am a little biased.

The suspense and mystery elements of this drama are not anything too unique, which is absolutely not an issue. It was done well enough that it felt fresh.
The supernatural twist, the monkey wrench in the villains' plans and the heroes lives, was also not terribly unique. But the way the characters moved through the story and interacted with the unbelievable was what really made this drama shine.

However, the really golden arc of this story started, in my opinion, a little late. When the main characters, whose interactions and fully-dimensioned identities were already so wonderful on their own, finally started to gel as a cohesive cast we were already well over the halfway point. What followed was some of the most exceptional character-driven storytelling I've seen in a while, I just wish the writers had chosen to get us there sooner. This drama would have worked better with another four episodes. As it is the last episode, while very satisfying, did feel rushed and also felt like several large explanatory pieces has been cut out for economy.
So much time was spent with our cast getting their bearings in a really confused and disjointed situation that we actually didn't get that long to really break down the characters besides the two main "brothers." I would have really liked to get as deep into the mind of Oh Man Suk's character, for example. He was fascinating and delicately written but ended as still almost a stranger.

Among the points I'd like to gush about: Jung Woo as Yook Dong Joo. What a performance. This character was one of those types of people who could have easily been very unlikable even if the writers had attempted to write him as likable. Yet both Jung Woo's interpretation and the meticulously written character development made him not just likable but admirable. He was pleasant to watch and behaved constantly in a way that stunned me. One of those really rare people with genuinely unpretentious integrity. I have a deep appreciation for characters who take responsibility for their actions. This is something you see done often and very deliberately in Korean and Chinese television and I love it. But the nuanced care that was taken in the way Yook Dong Joo owned his actions and their consequences was really impressive to watch. It is not easy to make a character who made the choices Dong Joo made genuinely likeable, but they did it. Moreover, his development in this regard was woven into the development of the plot. That was done really well and for that reason I understand why they let it take so long. And why I think this drama was too short. A few more episodes would have made it one of my favorites.

Examining the painful realities of their situation was one the things this story did really well. And again, they spent a lot of time on it. So much so that I felt they were hurried in the end to get the actual plot wrapped up. A lot of details were explored that are often overlooked in plots like this. I appreciated and enjoyed every minute of it. Every actor really did a great job.

As it is, I highly recommend this drama. You might find some parts of the first half a little frustrating, but the second half will more than make up for it.