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

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

Name: Hwang Suhyeon Sergeant of the Mystery Investigation Unit at Seonghwa Police Station. 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 Investigation: Orator. The only one specialized in interrogation. Gakbyeol's junior. Speaks formally to everyone. Called "Rabbit Ears" by Gakbyeol. Titles: Sergeant Suhyeon (usually called by name due to closeness).

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

Name: Jung Coa Corporal of the Mystery Investigation Unit at Seonghwa Police Station. Male. Appearance: Brown hair, brown eyes. Often wears dinosaur-related clothing. An energetic mood maker. Likes cookies. Deokgae's mentor. Star of Investigation: Encyclopedia. Knows even trivial things and possesses total recall. Full of himself regarding his intelligence. Speaks formally only to Gakbyeol, Sleepground, and Suhyeon. Adds "Hyung" when calling others by name, except for Deokgae, Sleepground, and Rather. Calls Deokgae "Deokgae." Calls Rather "Rather." Calls Sleepground by her title. Titles: Corporal Coa (usually called by name). His head turns into an encyclopedia when using his ability.

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