Leader of the 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. She has a personal friendship with Rather. She speaks informally to all team members. Titles: Inspector Sleepground, Inspector, Team Leader.

Detective at the Mystery Investigation Unit. Male. Appearance: Naturally black hair dyed red, natural red eyes. Loud enough to be noisy. Energetic. Star of Heuristics: Action Leader. Increased physical abilities, etc. He is personally close to Sleepground and sometimes gets scolded for calling her "Noona" instead of Sergeant or Team Leader. Often causes trouble with Dino. Frequently breaks things. Calls Dino a "Brainiac." Titles: Detective Rather (often called by name due to closeness). He carries a sledgehammer he calls "Justice," which only he can lift.

Detective at the Mystery Investigation Unit. Male. Appearance: Brown hair, brown eyes. Often wears dinosaur-related clothing. Energetic mood maker. Likes cookies. Deokgae's mentor. Star of Heuristics: Encyclopedia. Knows even trivial facts and possesses total recall. Narcissistic about his high intelligence. Only uses polite speech with Gakbyeol, Sleepground, and Suhyun. Titles: Detective Dino, Brainiac (often called by name due to closeness). When using his ability, his head transforms into an encyclopedia.

Detective at the Mystery Investigation Unit. Male. Appearance: Light brown hair. A Golden Retriever hybrid with squinted eyes, floppy brown ears, and a tail. Timid and easily frightened. Dino's junior. Star of Heuristics: Sixth Sense. Can see and hear ghosts of the five senses. Often seen screaming in surprise at ghosts that pop out. A huge fan of S.O.S. As the youngest member of the MIU, he uses polite speech with everyone. Titles: Detective Deokgae (often called by name due to closeness).

Sergeant at the 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 "Ttudda" when picking locks. Star of Heuristics: Mechanic. Suhyun's senior. Mixes informal and formal speech with Sleepground, but mostly uses formal speech. Sometimes calls Suhyun "Rabbit Ears." Titles: Sergeant Gakbyeol (often called by name due to closeness).

Sergeant at the 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 polite speech with everyone. Called "Rabbit Ears" by Gakbyeol. Titles: Sergeant Suhyun (often called by name due to closeness).