Sung Dong-il

Sung Kyu-Jin

Ho Taek

Do Won-Il

Kang Tae-shik

Jeong Sang-cheol Dawon as young Jeong Sang-cheol

Tes/Oh Joo-myung: Oh Soo-jeong's grandfather. A genius and compassionate cardiothoracic surgeon before he died in his 60's. Twenty years after his death, he still wanders the hospital as a ghost, helping the patients by possessing the hospital staff, including Cha Young-min while in his residency.

Park Hyeong-do

Jo Dae-jin

Ahn Dong-il/Peter, Jeong-won's eldest brother.

Jin Jong-hyun, forest chairman.

Go Dong-kook, a veteran detective with uncanny instincts who is assigned to Woo-hyun's case.

Ki Han-sol

Sa Ma-ryong

Han Se-sang, a down-to-earth chief judge with years of experience and knowledge who understands the harsh realities of life.

Chief Jo Ji-ho

So-so's boss

Lord Kim Wi-hwa

Ma Dae-young / Yang Seung-gil

Oh Jung-hak – former Crisis Negotiation Team leader

Grand General Park Soo-kyung

Professor Park

A fraud and security specialist at a bank, Dong-il fell into debt after lending money to a friend who never paid it back. He struggles to provide for his family as he wants to while paying off the debt, but does his best to give everything he can to his children. He and his wife, Il-hwa, argue a lot but love each other very deeply.

Yang Cheol-gon, a police inspector at the time of the original murders, and is now a well-decorated officer. Upon receiving his latest promotion, he surprises his superiors by requesting to be assigned back to Iltan, because he wants to end his career by capturing Gap-dong. Still convinced that Moo-yeom's father was the killer, he is extremely prejudiced against Moo-yeom, which makes for a combative working relationship. He also hiding grief of his daughter's death.

Jo Dong-min

Park Joon-han

Bong-goo, a slave of Saboksi who later becomes Jeon Woo-chi's loyal servant.

Kang Kyun-sung as young Dong-il in 1968 (ep. 9)

Jo Jung-goo

Ban Doo-hong

Chun Ji-ho

Nakamura Hwang

Lee Seung-jae

Lee Tim Chang

Jung Seung-gyu, Karl's manager/friend

Airline passenger

Jung Taek-soo

Kang Pil-bo

Mr. Can, Gangster leader's assistant

Ahn Yoon-gi