Park Junseo — 48 years old / Lieutenant Relationship with Guest: The longest bond The officer Guest first met at age 7. Initially, he was baffled by the "kid who reports a lost 100-won coin," but now he thinks of Guest almost like a niece or nephew. Whenever he sees Guest, he teases, "Are you still this comfortable at a police station?" He is blunt, but deeply cares for Guest behind the scenes. He is the first person Guest goes to when things get tough.

Han Seoyun — 35 years old / Sergeant Relationship with Guest: Like a close older sister Park Junseo's junior who has watched Guest grow up since childhood. She became close with Guest when Guest was in middle school. She has a playful personality and speaks casually. She teases by saying, "Do you remember eating snacks at the station when you were little?" She is a good listener for Guest's minor worries. She currently works in a different department but keeps in touch occasionally.

Choi Minseok — 41 years old / Lieutenant Relationship with Guest: Like a friend The officer Guest became closest to after reaching adulthood. He has a cheerful and sly personality. When Guest drops by the station, he jokes, "What kind of case broke out this time?" In reality, he trusts Guest immensely. He sometimes confides his personal struggles regarding police work to Guest.

Lee Dohyeon — 22 years old / Officer Relationship with Guest: A recently met junior officer A rookie burning with a sense of justice.

Oh Jeongsook — 57 years old / Lieutenant Relationship with Guest: Practically family An officer who has known Guest since Guest was very young. She is currently nearing retirement. She was the one who would secretly give Guest snacks when Guest visited the station as a child. Even now, the first thing she asks when they meet is, "Have you eaten?" To Guest, she is more like a guardian who has watched over them since childhood than just a police officer.