Woo Tae-seok – Starring Shin Ha-gyun

SNS team leader
He is a born detective who has the top criminal arrest record in Korea. He crosses the line, causing trouble all the time and is the ticking time bomb of the serious crime squad at Cheongin Metropolitan Police Agency. When he had first become a police officer, he made a mistake in judgment and ruined the life of a young high school girl, who goes missing after the Incident. This leads to a lifetime of regret and he becomes a bad cop who doesn’t hesitate to break the law to catch a criminal. He meets Seon-jae as a suspect of her parents’ murder and secretly starts working with her on a serial murder case. But, he cannot figure out if she is helping him or trying to lead him astray.

Eun Sun-jae – Starring Lee Seol

Local news reporter at Myunggang Ilbo, and psychopath
One word to describe Sun-jae is “genius”. She doesn’t feel anything, but is good at fooling people with her intelligence and manipulating people. This makes her crueler than most. Tae-seok, who has a dark violent side and is hiding his insanity which could surface anytime, shares a lot in common with Sun-jae. She admits Tae-seok is worthy and believes she has the sole right to ridicule, test and abuse him. She finds joy in anticipating Tae-seok’s reactions. This is why she decides to help him, whether he realizes it or not.

Jeon Choon-man – Starring Park Ho-san

Leader of the police investigation team at Cheongin Metropolitan Police agency
He has a bad relationship with Tae-seok and is an enemy within the agency. He met Tae-seok when he was an instructor at the police academy and liked Tae-seok, who was smart and stuck to the rules. He planned to catch the murderer of Kwon Soo-ah and take credit through Bae Yeo-wool, the witness Tae-seok found. However, he finds out that the suspect Jang Sun-ho(Jang Hyung-min)’s parents are highly influential in the local community and close to the police chief. He cross-examines Yeo-wool and Sun-ho, saying that’s the rule. Later, Tae-seok finds out Choon-man is corrupt and reports him, making their relationship worse.

Jang Hyung-min – Starring Kim Gun-woo

Prosecutor at Cheongin Prosecutors Office, serial killer, changed his name to Jang Sun-ho
He is the murderer who left an inerasable scar on Tae-seok’s heart. He is assumed to have killed Kwon Soo-ah, a schoolmate, 13 years ago. To avoid Tae-seok, the only person who figured out who Hyung-min is, he changes his name to Jang Sun-ho and starts murdering more people. He becomes a prosecutor and leads a double life, slipping through the fingers of justice, using warrants and indictments, privileges of a prosecutor. However, he meets Tae-seok again when he is appointed to the Cheongin District Prosecutors’ Office and the two men start trying to outsmart each other once more.