Song Young-gyu

as Ryu Gwang-pil (1 episode)

as Kim Min-jung (12 episodes)

as Yoon Se-hoon (8 episodes)

as Song Young-sik (1 episode)

as Detective Chief

as Choi Yong-nam

as Yoon Hak-young (16 episodes)

as [Institution director] (6 episodes)

as Park Jong Su (6 episodes)

as Jeong Kyung-han

as Han Je Moon

as Baek Yeong-cheol

as Janitor

as Kwak Moon Heum (16 episodes)

as Gui-nam

as Ma Seok-koo (16 episodes)

as Oh Sang-hoon (1 episode)

as Detective Squad Chief Choi

as Jang Cheol-Min (32 episodes)

as Police University Professor (32 episodes)

as Ma Do-Nam (64 episodes)