The legendary killer 'Biguang' who died due to his organization's betrayal. Reincarnated in the body of police officer 'Kim Gyeongsu', he vows revenge against Hwaguksa, the killer organization that betrayed him. He is the reincarnation of December Biguang, Hwaguksa's legendary killer. He moves to take revenge on Yu-hwa, his enemy from his past life. He started as a patrol officer but was promoted to corporal after single-handedly wiping out a gang involved in a drug deal at a nightclub. Since reincarnating as Kim Gyeongsu, he displays combat power comparable to his past life as Biguang, thanks to Gyeongsu's well-trained body. Biguang even noted that with a bit more training in this body, he could surpass Yu-hwa. Upon waking up, he found himself reincarnated as Kim Gyeongsu, a patrol officer at Ilsan Police Station. {As Biguang, he was taken in by a shaman as a child and raised as a killer. He believed the promise of freedom after his final mission (wiping out the Truth Sect), but was betrayed and murdered. He appears to have been the most skilled among the 12 Months.} No one knows he is a reincarnated soul except for Hong Jun.

Real Name: Jo Gyeonghui Age: 25 Nationality: Republic of Korea Affiliation: Gyeonggi Ilsan Police Station (Patrol Officer) Occupation: Police Officer She is the physically weakest among the patrol officers, but she is exceptionally brilliant, ranking 1st in both written exams and interviews. Unlike the other two patrol officers, she has the grit to stay in the police force. Furthermore, there are many mentions of her potential shining through while being trained by Kim Gyeongsu. She is quite beautiful.

Real Name: Hong Jun Nationality: Republic of Korea Family: Hong Yeon (Daughter), Beodeul Affiliation and Rank: Commissioner of Gyeonggi West Provincial Police Agency (Superintendent General) Occupation: Police Officer Maybe a candidate for the 'Ojicon' (attraction to older men) trope(?)

Real Name: Hwang Huijun Age: 25 Nationality: Republic of Korea Affiliation: Gyeonggi Ilsan Police Station (Patrol Officer → Corporal) Occupation: Police Officer He is a black belt in grappling-based martial arts like Judo and Jiu-Jitsu, but he is a total coward. He is definitely ranked above Lee Seonghyeon.

Real Name: Lee Seonghyeon Age: 25 Nationality: Republic of Korea Affiliation: Gyeonggi Ilsan Police Station (Patrol Officer → Corporal) Occupation: Police Officer Like Hwang Huijun, he is a black belt in grappling martial arts like Judo and Jiu-Jitsu, but he is a coward. He is definitely ranked below Hwang Huijun.