Lee Soo-hyuk

Police officer(Ep. 1)

Cha Joo-ik

Cha Hyung-bin / Kim Soo-hyuk

Mr. Myeong (season 2, Ep. 6–7)

Choi Chan-gyu – An aspiring police officer, Chan-gyu takes any job in order to take care of his father and brother. After seeing how Chan-gyu has athletic abilities (when he outran the guards at the police entrance exam), he is hired by Tae-Ho to secretly monitor a few targets who later end up dead. Because of this, he becomes a prime suspect for the disappearances, but is later vindicated. He discovers Shi-yoon's alter ego as the Shadow and asks him to train him. He has a crush on Writer Bae. In the end, he becomes a police constable.

Choi Geon-wook / Gary Choi Hong Dong-young as young Geon-wook

Kwon Deuk-bong

Gwi

Kim Joon - Found by his grandfather at his doorstep, Kim Joon grew up following his grandfather's footsteps by becoming a carpenter. He hired someone to be the painter for his new studio and did not expect it to be a girl. At first being cold and grouchy with Il-ri and her chattering, he later fell in love with her even with the knowledge of Il-ri being married.

Yoo Jin-woo

Kim Soo-hyun, prosecution office's investigator.

Lee Soo-in

Soo-hyuk/Mukadil Paejua

Yoon Pyeong Baek Su-ho as young Pyeong

Yoon Soo, a mysterious and eccentric rich boy with a love of music.