This drama is the first K crime drama focus that I really really like. This drama is truly a masterpiece. Each episode always hooks me and keep me going. I don't even skip any scene. Which amazing and surprising. I really enjoy the whole journey. Each character was very lovable. Each episode has a lot of meaning and just perfect. I don't think I can find any fault with this drama.

I came to really like Choi Jin Hyuk. I hope he will play in more drama as the main character. He is a very excellent actor and him always able to make his character to be cute and loveable. Not only him, all the actors and actresses are doing a great job in their acting skill and building the chemistry.  Park Kwang Ho and Sun Jae have been on my high list of my fav bromance after all!!

This drama is based on a real-life case of Hwaseong serial killer. Many crime drama and film are made based on this incident. Recently I watched Gap Dong, which is also based on the same incident. However, I feel that Tunnel has been able to grasp the case and foretell it in a way-way better than Gap Dong.  The way they tell the case, the set of the victims and all other things was a work of art. Like if you notice, when he go to the past, the color of the scene has a tone of Sephia, whereas in the future has a tone of blueish to confirm its in the future.