Regular Cast (Description):
Kim Se-Jeong (Student/Youngest Member of K's Detective)
Guest Star (descriptions):
Jang Gwang (K's Longtime friend) -- Kriesha (The Gentleman's Secretary) -- Ppak-gu: (43 - A legendary serial diamond thief/Locked himself up and is living in a container) -- Agency CEO Ahn Il-Gwon: (Was a manager who tried to sign a contract with the victim Jang Mi-Ra/ Currently a CEO of an Agency) -- Crazy Piano: (Occupation: Unemployed - former Composer/Got a bad reputation after getting accused of a plagiarism and stopped composing) -- Seo In-Ah (39 - A faceless singer who sang instead of the victim Jang Mi-Ra/ Was jealous of Jang Mi-ra)
Kim Se-Jeong (Student/Youngest Member of K's Detective)
Guest Star (descriptions):
Jang Gwang (K's Longtime friend) -- Kriesha (The Gentleman's Secretary) -- Ppak-gu: (43 - A legendary serial diamond thief/Locked himself up and is living in a container) -- Agency CEO Ahn Il-Gwon: (Was a manager who tried to sign a contract with the victim Jang Mi-Ra/ Currently a CEO of an Agency) -- Crazy Piano: (Occupation: Unemployed - former Composer/Got a bad reputation after getting accused of a plagiarism and stopped composing) -- Seo In-Ah (39 - A faceless singer who sang instead of the victim Jang Mi-Ra/ Was jealous of Jang Mi-ra)
In Ahn Il-Gwon's office, Jong-Min and Jae-suk find a Gududu CD. Kim Se-Jeong is part of this Kpop girl group.
The murder victims song "You're the Only One for Me" is sung by Kim Se-Jeong. That is why Park Min-young gives the camera an amused look when Se-Jeong plays the cassette at the crime scene. At the end of the episode, they show her recording the song in the studio.