Psycho Face

15 years ago, Kwon Kyeong-Chan is chasing the murderer who killed his sister. He becomes a police officer and hides his identity, chasing various evil faces that walk the world under the name of 'Black Sheep'. If he catches bad guys, he will eventually meet 'that guy' who killed his sister. He tracks down the criminals' activities without regard for the means and methods for revenge. He starts to cooperate with detective Kang Cheol-Ho, who is more gangster than gangster, and begins a full-scale chase. That guy starts to move again

(Source: KakaoPage, translated)