Likes
1. Really intense, tightly written drama. Great acting from everyone, esp Yoon Si Yoon and Choi Seung Yoon
2. Very unpredictable story, that kept me guessing not only about the killer, but what will happen next and how it will end. Just when i thought i know who the killer is, the drama surprises us with one big twist after another. And another. Ive never been so happy being so wrong and looking forward to the next episode with my mouth hanging open from disbelief and amazement.
3. Due to the shorter episodes, there were several questions that were left unanswered, esp on how you can cross boundaries and the ending, but it didnt deter me from enjoying the story because this drama didnt focus on how you cross worlds. From the start it was all about the characters and how the consequences of their actions can change their world.

Dislikes:
1. When they revealed the killer, it was so twisted and sick i wanted to steal Seokyung's gun and just end the killer's misery. The conversation between the killer and Dowon was shocking. I had the same expression of "no it cant be you're kidding!" on Dowon's face.
2. The ending was left to our imagination, but felt like it was "too nice" of an ending from a very grim drama.

Rating: 9/10