This story will tell the viewers about a man whose name is Yook Dong Shik who accidentally witnessed a murder and loses his memory after an accident happened while he's fleeing the scene. Eventually, he wakes up with no sense of any self-identity and he mistakes himself as the psychopathic killer when he found out about the murder's diary in his hands.

Yoon Shi Yoon will be the one who has taken on the role of Yook Dong Shik, he shared "I took on the role of the pushover of pushovers who thinks he's a psychopath." After this, he explained that his character will work at a securities investment firm and is at the bottom of the social ladder. Unfortunately, after going through an unusual experience that leads him to mistake himself as a psychopath and he's no longer afraid to say things on his mind and starts to speak for himself. The actor continued to share, "This is the most fun to play out of the roles I've played recently, but the character's also very silly. I chose it because I believed I could do something fun with it."

Looking forward to the character of Jung In Sun who took on the role as Shim Bo Kyung who is a patrol officer who lives solely in the present time, then she explains that her character would intentionally be involved in a mysterious case and begins to solve the case in partnership with Yoon Dong Shik. She added that it was fascinating for her on how her role has a gap between her actual life and the ideal world itself.

Moreover, Park Sung-Hoon will be the one to play the role of Seo In Woo who is the real murderer in the story. He described his character as the director of Daehan securities firm who's detailed and confident and the real owner of the diary that Yook Dong Shik had. He stated, "I wanted to take on the role because I believe this character has many different sides of himself unlike other psychopath roles from before." He also shared that he is all excited about showing off a bromance with Yook Dong Shik.