Supporting
Krystal Jung as Kim Ji-ho
Shin Rin-ah as child Kim Ji-ho
Lee Chae-yoon as teenage Kim Ji-ho
Je-hyuk's girlfriend who is a traditional Korean medicine student.
Lim Hwa-young as Kim Je-hee, Je-Hyeok's younger sister
Ye Soo-jung as Je-hyuk's mother
Kim Kyung-nam as Lee Joon-dol
Joon-ho's younger brother who is a reporter and an avid fan of Je-hyuk.
Sung Dong-il as Chief Jo Ji-ho
A veteran chief prison guard who is quick and flexible when it comes to resolving incidents that take place inside the prison, but is known for being corrupt and easily swayed by money or other material goods that inmates can provide him.
Jung Jae-sung as Professor Myung
Lee Ho-chul as Gal Dae-bong (a.k.a. "Seagull")
Choi Moo-sung as Kim Min-chul (a.k.a. "Long-term Prisoner")
Park Ho-san as Kang Chul-doo (a.k.a. "KAIST")
Lee Kyu-hyung as Yoo Han-yang (a.k.a. "Second-generation Chaebol" or "Looney")
Jung Hae-in as Yoo Jeong-woo (a.k.a. "Captain Yoo")
Jung Min-sung as Go Park-sa (a.k.a. "Doctor Go")
Kang Seung-yoon as
Lee Joo-hyung (a.k.a. "Jean Valjean")
Kang Seung-yoon as Lee Jong-won, Min-chul's fellow gang member who strongly resembles Joo-hyung. He, Min-chul and three others were found guilty of the murders of two rival gang members, but unlike Min-chul and two of their fellow co-accused, Jong-won (together with their gang leader) was sentenced to death and executed on 6 January 1996.
Kim Sung-cheol as Kim Young-cheol (a.k.a. "Jailbird"), A man who frequently goes in and out of prison and the first person in the prison Je-hyuk befriends. Je-Hyeok pays for Young-cheol's mother's surgery. He is recruited by Je-Hyeok after his prison term.
Ahn Chang-hwan as Dong-ho (a.k.a. "Croney")
Jung Woong-in as Assistant Chief Paeng Se-yoon
