Yu Oh-seong

as Jeong Doo-cheol (10 episodes)

as Cheol-soo's father

as Jo Sang-tae (16 episodes)

as Gil Seok / Chairman Oh

as Baek Mo-sa (12 episodes)

as Tak In-hwan (16 episodes)

as Seo-geom (16 episodes)

as Yeon Gaesomun

as Seo Jong-Gil (36 episodes)

as [Teacher]

as Self

as Choi Hyeon-joon (20 episodes)

as Gil So-gae (41 episodes)

as Choi Gook Jin (1 episode)

as Choi Ki-hoon

as Hwang Ki-chul (16 episodes)

as Choi Won-shin (22 episodes)

as Joon-seok

as Detective Oh

as Ki Chul (24 episodes)

as Self (1 episode)

as Trainer Yoon

as Shingwi Ghan / Tae-gang (32 episodes)