Narrative Arc and Key Twists:
The story opens with Detective Ma Seok-do joining Seoul's Metropolitan Investigation Unit. When investigating the death of Go Sun-hee, who fell from a hotel window, autopsies reveal high concentrations of "Hiper," a lethal synthetic drug manufactured in Japan.
The Double Twist:
The drug ring is masterminded by Joo Sung-cheol, who is actually the chief of a local police Narcotics unit. Joo murdered an undercover detective trying to blow the whistle. Joo has been collaborating with Tomo, a Seoul-based Yakuza representative, to steal 20kg of Hiper from Japanese Yakuza boss Chairman Ichijo. Joo intends to double-cross the Yakuza and sell the stolen stash to a Chinese Triad syndicate for $30 million.
Discovering Tomo's treason, Chairman Ichijo dispatches his deadliest katana assassin, Riki, to Seoul. Riki executes Tomo and hunts for the hidden 20kg stash. Joo attempts to play all sides, using his police authority to track Riki while trying to complete his secret deal with the Chinese Triad.
Climax and Resolution:
Using information extracted from club owner informants and Cho-rong, Ma Seok-do tracks down the location of the drug exchange. Riki ambushes Joo and captures the drugs, but Ma arrives at Riki's hideout. In a showdown, Ma takes minor sword cuts but brutally knocks out Riki and his sword-wielding goons using heavy boxing body blows and hooks.
Ma then tracks a cornered Joo Sung-cheol back to his office at the police station. Joo tries to bribe Ma and then attacks him with a knife, but Ma completely demolishes Joo—punching him through office desks, walls, and glass partitions. Joo is arrested, the corrupt narcotics team is dismantled, and Seoul’s streets are secured. In the mid-credits scene, Ma visits Jang I-soo to enlist his help for another upcoming investigation.