Yui Kazama, the current Sukeban Deka, finds herself working for a new government initiative known as the Juvenile Security Bureau. This elite organization, led by the charismatic yet ruthless politician Kuraudo Sekine, is designed to combat escalating juvenile crime with extreme prejudice. Sekine has equipped his young agents with lethal triple-bladed yo-yos and sanctions brutal tactics, including summary executions. Uncomfortable with the bureau's increasingly zealous and violent methods, Yui refuses to participate in an undercover mission and formally resigns, hoping to return to a normal life with her older sisters, Yuka and Yuma.

Her retirement is short-lived. Yui discovers that Sekine and the Juvenile Security Bureau are not merely overzealous; they are fundamentally corrupt. The bureau has been staging a series of terrorist attacks and framing a innocent gang of juvenile delinquents known as the Outcast League. As the Kazama sisters dig deeper, they uncover the chilling truth: Sekine’s ultimate goal is to use his private army of student agents to overthrow the Japanese government in a violent coup d'état.

Forced back into action, Yui realizes she cannot stop Sekine's conspiracy alone. She and her sisters, each wielding their own unique unconventional weapons, form an uneasy alliance with the very outcasts the bureau has been trying to eliminate. Together with the outcasts’ disenchanted leader, Kei, the Kazama sisters become the last line of defense. They launch a desperate counterattack against the corrupt bureau, engaging in a high-stakes battle across land, sea, and air to expose the conspiracy and save Japan from descending into tyranny.