This is the real-life origin of the film’s premise.
Given the gritty realism of Korean cinema (think Memories of Murder or The Chaser ), it is a natural instinct to ask if this shocking narrative was ripped from the headlines. The short answer is is the gangster the cop the devil based on true story
However, one detail the film borrows accurately is the . In the movie, the gangster (Don Lee) deliberately rams his car into the killer's vehicle to disable him. In reality, Yoo Young-chul was caught because he rammed his car into a police surveillance vehicle by accident, leading to his arrest. The filmmakers inverted this—giving the gangster the agency to crash the car. Fact vs. Fiction: The Definitive Split To help clarify, here is a direct comparison between the film’s plot and the historical reality: This is the real-life origin of the film’s premise
Furthermore, the "mob boss" Kim Tae-chon never entered into a formal alliance with the police. Kim was arrested shortly thereafter for his own crimes (including violence, blackmail, and running gambling dens). He only told the story about beating up the serial killer to the press after he was in prison, likely to boost his reputation. In the movie, the gangster (Don Lee) deliberately
In reality, Kim Tae-chon just beat the guy and let him go. That makes for a funny anecdote, but not a two-hour thriller.