Azuma is a police detective who lives with his Akari, his cognitively challenged sister whom he protects fiercely, and he bears a heavy gambling burden that constantly drags him into debt. He also has a strong sense of morality and a reputation for using excessive violence with criminals, often bending or ignoring police rules when they get in the way. For example, after witnessing a gang of teenage boys beat a homeless man for amusement, he goes into the gang leader’s home, administers a brutal beating, and then extracts a promise that the leader will surrender himself and the others the next day. his superiors, impressed by his results, tolerate his frequent rule-breaking by making him write apologies whenever he commits an unlawful act.
Azuma and his new partner Kikuchi are assigned to investigate the murder of a drug dealer and to disrupt a drug deal in a nightclub bathroom. The seller, who works for yakuza boss Nito, names Iwaki, Azuma’s close friend and fellow detective, as his supplier. Azuma is pressed to help locate Iwaki, who seems to have vanished as newspapers reveal his ties to the yakuza; a fisherman later finds Iwaki’s body hanging from a noose under a bridge. Refusing to accept that his friend would take his own life, Azuma sets out to track down the dealers from before, but both men are executed by the sociopathic yakuza hitman Kiyohiro. Unable to take action against the well-connected Nito, Azuma plants drugs in Kiyohiro’s apartment, captures him, and tortures him in the police station for information. This brutal act angers the deputy chief, who forces Azuma to resign to shield the force from a potential investigation.
Azuma spends his first day out of work doing as he pleases in town, but Kiyohiro and his men seize the opportunity to abduct Akari and take her to their hideout, where they subject her to repeated rapes and force-feed drugs to deepen her addiction. In a confrontation on a busy street, Kiyohiro defies Nito’s orders and tries to stab Azuma; Azuma grabs the knife, Kiyohiro pulls a gun, and a nearby bystander, a young woman, is accidentally killed when his shot misses. Azuma manages to stab Kiyohiro in the leg and escapes. The following day, he buys ammo and an unregistered firearm from a friend at the gambling parlor and trains himself, preparing for a decisive showdown.
Anticipating Azuma’s move, Kiyohiro orders his men to brace for a shootout, but when they balk, he executes two of them. The third attempts to flee, only to be gunned down by Azuma as he arrives. In the ensuing gunfight, Kiyohiro shoots Azuma multiple times, but Azuma ultimately kills Kiyohiro as he searches for more weapons. He is finally reunited with Akari, but she has become so completely addicted that she robs Kiyohiro’s corpse for more drugs. With his final bullet, Azuma mercy-kills her. A badly wounded Azuma staggers to leave, but he is killed by Shinkai, Nito’s former advisor, as revenge for Azuma killing Nito, who was believed to have ordered Kiyohiro to pursue Akari.
Sometime later, Kikuchi, now a senior vice detective, meets with Shinkai, who explains that with the heat surrounding Azuma’s actions dying down, he wants Kikuchi to take over for Iwaki and continue to traffic drugs through the police force. Kikuchi eagerly accepts Shinkai’s offer and leaves.
