In a near-future Japan, society is strictly governed by a human rights management system. Citizens must carry a rights card granting them access to social benefits, housing, and legal protection. Those who lose or surrender this card become mujina, individuals stripped of all rights and legal existence. While this status makes them vulnerable to discrimination and government hunting squads, it also renders them functionally invisible to the law, allowing them to operate as untouchable assassins for hire using specialized gear like nakamatsu boots that enable rooftop travel.

The story centers on Ubume, a thirty-year-old mujina assassin who works for an enigmatic broker named Nive. Skilled with an electrified katana, she accepts any job for cash while seeking a mysterious figure in a tanuki costume from her past. Her world collides with Terumi Morgan, a cynical game developer of Japanese and French-Canadian heritage who has resigned himself to meeting work deadlines and watching pornography in peace. When a sudden illness disrupts his routine, Terumi encounters a teenage runaway named Juno Oshima, who has fled her hometown after enduring bullying and neglect that left burn scars on her body. Ubume rescues Juno from a predatory pop star and, through a series of events, the three end up sharing Terumi's apartment as an unconventional found family.

The narrative conflict intensifies with the arrival of Tenko, a charismatic and sadistic young mujina who embraces her outlaw status as a badge of honor and flaunts her killings on social media. Tenko develops a violent obsession with Ubume, alternately expressing murderous intent and sexual attraction toward her rival. After Tenko deliberately disrupts one of Ubume's contracts, Ubume's standing with Nive plummets, leaving her deeply in debt and needing to prove herself again. She accepts a dangerous assignment to assassinate the Megidos, child abusers operating under the guise of media training and protected by a high-level mujina bodyguard.

As the series progresses, the world expands to include public safety officers Kashio and Yuhang, a mismatched duo assigned to Division 9 to hunt dangerous mujina with Ubume as their primary target. New mujina emerge, including Mai, a hostess who sells her rights for 200 million yen to buy the affection of a male host she loves, only to find she cannot reverse the transaction and spirals into drug use becoming an assassin herself. The elderly are also stripped of their rights at age eighty-five and shipped to senior zones to await death. Through these intersecting storylines, the series explores themes of social alienation, the commodification of human existence, generational conflict between those who see work as identity and those who measure worth through social media validation, and the question of whether true freedom lies outside the law or within it.