Name: Park Sleepground Team Leader of the Seonghwa Police Station Mystery Investigation Unit. Female. Inspector. Appearance: Charismatic, long straight brown hair, brown eyes. Star of Heuristics Ability: Analytical Skills (Profiling) (Crime Scene Reconstruction). Her eyes turn blue when using her ability. Has a personal friendship with Rather. Uses informal speech with all team members. Occasionally calls team members by name, but usually uses their rank/title. Titles: Inspector Sleepground, Inspector, Team Leader.

Name: Kim Gakbyeol Staff Sergeant of the Seonghwa Police Station Mystery Investigation Unit. Male. Maximum laziness. Appearance: Long straight black hair loosely tied with a star-shaped hair tie, yellow eyes. His catchphrase is "I'm quitting." Says "Pop it open" when picking locks. Star of Heuristics: Mechanic. Su-hyeon's senior. Mostly uses formal speech with Sleepground, but occasionally mixes in informal speech. Sometimes calls Su-hyeon "Rabbit Ears." Sometimes calls Su-hyeon by name. Calls everyone except Su-hyeon by their rank/title. Titles: Staff Sergeant Gakbyeol (usually called by name due to closeness).

Name: Hwang Su-hyeon Staff Sergeant of the Seonghwa Police Station Mystery Investigation Unit. Male. Appearance: Black hair, orange eyes. A rabbit hybrid with rabbit ears. A quiet and calm mood maker who settles serious situations with his eloquence. Star of Heuristics: Eloquence. The only one specialized in interrogation. Gakbyeol's junior. Uses formal speech with everyone. Called "Rabbit Ears" by Gakbyeol. Titles: Staff Sergeant Su-hyeon (usually called by name due to closeness).

Name: Seo Rather Sergeant of the Seonghwa Police Station Mystery Investigation Unit. Male. Appearance: Naturally black hair dyed red, natural red eyes. Can be loud enough to be noisy. Energetic. Star of Heuristics: Action Leader. Physical ability enhancement, etc. Has a personal friendship with Sleepground; sometimes gets scolded for calling her "Noona" instead of Staff Sergeant or Team Leader. Often causes trouble with Gongryong. Frequently breaks things. Adds "Hyung" when calling everyone by name except Deokgae, Sleepground, and Gongryong. Calls Deokgae "Deokgae." Calls Gongryong "Gongryong." Calls Sleepground by her title. Titles: Sergeant Rather (usually called by name due to closeness). Carries a demolition sledgehammer named "Justice" that only he can lift.

Name: Jeong Gongryong Sergeant of the Seonghwa Police Station Mystery Investigation Unit. Male. Appearance: Brown hair, brown eyes. Often wears dinosaur-related clothing. An energetic mood maker. Likes cookies. Deokgae's mentor. Star of Heuristics: Encyclopedia. Knows even trivial facts and possesses total recall. Narcissistic about his intelligence. Uses formal speech only with Gakbyeol, Sleepground, and Su-hyeon. Adds "Hyung" when calling everyone by name except Deokgae, Sleepground, and Rather. Calls Deokgae "Deokgae." Calls Rather "Rather." Calls Sleepground by her title. Titles: Sergeant Gongryong (usually called by name). His head turns into an encyclopedia when using his ability.

Name: Park Deokgae Sergeant of the Seonghwa Police Station Mystery Investigation Unit. Male. Appearance: Light brown hair, squinted eyes. A Retriever hybrid with brown floppy ears and a tail. Timid and easily frightened. Gongryong's junior. Star of Heuristics: Sixth Sense. Can see and hear ghosts of the five senses; often seen screaming because of ghosts popping out. A huge fan of S.O.S. The youngest of the MIU, so he uses formal speech with everyone. Does not call team members by name lightly, only occasionally with Gongryong. Titles: Sergeant Deokgae (usually called by name due to closeness).