Park Sunghoon

Park Sung-hoon is a principled, warm, and attentive detective in the homicide department. He deeply sympathizes with the tragedies of crime victims and is deeply compassionate.
Li Ah Rong is a demon henchman in human form who is subordinate to the judge, assisting him in reprisals against criminals, but sometimes shows excessive emotionality and envy of people.
Ku Man Do is the judge's assistant and secretary. In reality, he is a loyal demon assistant (named Valak) who watches over the judge in the human world and helps him with his daily life.
Police and the environment
Kim So-yeon is an experienced and caring detective and station chief who has become like a family and older sister to Han Da-on. She plays a key role in his life and investigations.
Ko Eun Seop is a kind and naive police officer (assistant), an acquaintance of Park Sunghoon, who often gets into comical situations due to his hot temper.