The film starts with Ami Hyuga killing a group of bullies who were picking on a guy. After she eliminates the bullies, she tells him the story of her life before she became what she is. She was just an average high school girl, trying to lead a normal life. Her world came crashing down when her brother and his friend are killed by the members of the yakuza and their young leader. As Ami tracks down the ringleader, she is surprised to discover the bullies' association with a sinister ninja yakuza family. When she goes after her revenge, she soon finds herself in over her head and minus her left arm. Barely surviving, Ami escapes and seeks out shelter from two kindly garage mechanics, the parents of her brother's friend. They take pity on her, fitting her with a high-powered machine gun where her arm used to be. She then teams up with the chainsaw-wielding mother of her brother's slain friend and together they unleash an unholy, non-stop kill fest against the killer of their loved ones.