A nondescript home improvement store in a quiet town hides a dark secret. Its manager, Karasuma Akane, runs a secret revenge service on the side. People who have been wronged by criminals who escaped legal punishment—stalkers, murderers, loan sharks—come to her seeking justice. Akane listens to their pain and designs custom revenge devices, each one tailored to the specific crime. With help from her store clerk Kinjo, she captures the targets and forces them into deadly games where the only way to survive is to face consequences that mirror their own sins. A stalker is strapped into a chair and given a choice: cut off his own manhood or be burned alive. A teenage killer who drowned a little girl is locked in a water tank and must navigate barbed wire to escape. A loan shark is made to navigate a maze of pipes to collect money, with electrocution as punishment for a wrong move. As Akane continues her work, she draws closer to a figure known only as 1DK, a serial killer responsible for her parents' death. The morality of her actions is never simple—she offers her targets a chance to repent, but only the truly desperate take it. The manga unfolds as a series of self-contained revenge arcs, each one posing the question of where justice ends and vengeance begins.