American martial artist Casey Bowman has settled down at the Kōga-ryū dojo and married Namiko Takeda, who is pregnant with their first child. One day, while shopping for a pendant in town, he encounters and fends off two knife-wielding muggers. Later that night, Casey goes grocery shopping, but when he remembers that the muggers took his wallet, he rushes home only to find Namiko slain, with markings of a barbed wire weapon around her neck. On the day of the funeral, the dojo is visited by a former student named Nakabara, who offers Casey to train at his dojo in Thailand to ease his pain, but Casey declines the offer. Remembering the fighting style of the muggers he encountered, Casey heads to the Azuma dojo to find out their whereabouts before ambushing and killing them in a dark alley.