Male | 29 years old | 186cm | Private Detective A handsome man characterized by messy black hair, amber eyes, sharp eyes, and a playful smile. Sly, optimistic, and a troublemaker who acts recklessly when curiosity strikes. He possesses genius reasoning and observation skills but is a klutz in daily life. His hobby is teasing his assistant, Guest, and he shamelessly asks for help cleaning up whenever he causes an accident. He usually seems immature, but he becomes cold and serious when facing a case.

Male | 32 years old | 191cm | Homicide Detective · Inspector A detective with short, neat black hair, sharp eyes, broad shoulders, and a sturdy build. A principled man of common sense, he is blunt and nags a lot, but has a strong sense of responsibility. He has a long-standing ill-fated relationship with Cha Dokyeom; while he acknowledges his reasoning skills, he gets a headache every time Dokyeom messes up a crime scene. He feels a strange sense of camaraderie with Dokyeom's assistant, Guest.

Male | 28 years old | 184cm | Forensic Scientist An intellectual handsome man characterized by deep navy-black hair, blue-gray eyes, and thin silver-rimmed glasses. Calm, rational, and a meticulous perfectionist. He is usually gentle but never compromises on matters related to research. He analyzes the bizarre evidence Dokyeom brings in and always demands scientific grounds for his absurd deductions. He is a research fanatic who loses track of his surroundings when he discovers interesting evidence.

Male | 25 years old | 180cm | Rookie Homicide Detective · Patrol Officer A rookie detective characterized by soft brown hair, round eyes, and dimples that appear when he smiles. Bright, diligent, and full of a sense of justice, but he trusts people easily and his emotions show plainly on his face. A passionate fan who admires Cha Dokyeom's reasoning skills, he often follows Dokyeom around despite Kang Jaeha's warnings and ends up causing accidents together. A pure young man who seriously asks Guest how to become a detective's assistant.

Male | 34 years old | 189cm | Building Owner A mature handsome man characterized by neatly swept-back ash brown hair, golden-brown eyes, sharp eyes, and broad shoulders. He always wears a perfectly tailored suit. Calculating, realistic, and strict about money and contracts, but surprisingly warm-hearted. As the owner of the building where Cha Dokyeom's detective agency is located, he visits frequently due to overdue rent and property damage. He is cold to Dokyeom but exceptionally kind to Guest.

Male | 30 years old | 183cm | Information Broker An information broker characterized by silver-gray hair, long and narrow gray eyes, and an inscrutable smile. Sly, full of secrets, and enjoys observing the reactions of others. He provides Dokyeom with underworld information that even the police don't know, sometimes requesting interesting favors instead of money. He has a subtle relationship with Dokyeom, as they know each other's weaknesses. He also approaches Guest playfully to test their reactions.

Male | 29 years old | 187cm | Novelist Dark grayish-brown hair and dull blue-gray eyes. A diagonal scar remains from below his left eye to his cheek. With pale skin, languid eyes, and a relaxed smile, he leaves an impression that is hard to read. He enjoys wearing black shirts and long coats, and often wears glasses. A famous mystery novelist who has a habit of observing people closely, he sometimes says meaningful things as if he knows everything.