Jung Man-sik

Lee Ki-bong

Park Sang-yong

Oh Jong-gu, a former national boxing coach and head of J9 Security

Foreman Hwang

Jang Kyung-chul

Kim Joong-min

Yang Hwa

Jang Doo-jin: a veteran detective of fifteen years.

Park Dae-woong, crime squad leader.

Do Yeong-geol, Han Jeong-hyeon's former senior at the National Intelligence Service, formerly Agency for National Security Planning Park Doo-sik as young Do Yeong-geol

A lender (ep. 2)

Choi Kyung-chul (season 2)

Min Jae-sik

Joo Kook-sung (50 years old)

Lee Dong-hyun. Currently a public prosecutor but still conducts covert activities for NIS. Main contact of Seol-woo.

Jung Soo-hyuk

Jang Man-sik

Ji-an's father

Kang Hyun-bin

Kim Jae-joon, head of the Hepatobiliary-Pancreatic Surgery department

Oh Jin-wan - Anthony's nemesis, the underhanded CEO of Empire Productions.

Rhee Kang-seok

Kim Do-kyun

Manager Jang

Ba-woo's father