Main Characters:

Lee Soo-Hyuk as Kim Soo-Hyuk (also Cha Hyungbin in 1980's)

Jin Se-Yeon as Jung Sabin (also Jung Haeun in 1980's)

Jang Ki-Yong as Chun Jongbum (also Gong Ji-Cheol in 1980's)

Cha Min-Jee as Jae Yi a.k.a Jay

Secondary Characters:

Jang Won-Young as Detective Joo In-Do

Han Hae-Rim as Yoo Seo-Young/Professor Yoo

Choi Dae-Chul as Seo Tae-Ha

Kim Do-Kyung as Jang Ma-Chul (Seo Tae-Ha's subordinate)

New Character's Introduction

Yang Se-Jong as Jang Ho-Jun

Character's Importance: Main Character

New Character's Description:

A young detective with a calm demeanor who transferred from Incheon to Seoul, and also a friend of Jae Yi since high school. He starts investigating an abandoned body's case, which leads him to suspect a criminal who had chances of being released on retrial. Comes across Soo-Hyuk by chance and befriends him later due to the turn of events.