Sasaki Rena, a woman with a sharp mind and photographic memory, becomes a private detective with a singular mission: to hunt down and eliminate corrupt private detectives. Her motivation stems from a personal tragedy—her younger sister was murdered by a stalker, and the stalker obtained her sister’s location from a private detective. Rena enrolls in a detective training school run by Suma Research Company, a mid-sized investigation firm. After completing her training, she is assigned to the company’s newly created Anti-Detective Section, a unit dedicated to rooting out and dismantling unscrupulous detectives who abuse their position for profit, blackmail, or violence.

The story is told largely through the eyes of Minemori Kotoha, a young woman who joins Suma Research as a novice and is placed in the Anti-Detective Section as Rena’s assistant. Kotoha is naive about the real workings of the detective industry, expecting the glamorous, intellectual work seen in fiction. Instead, she is thrust into a brutal reality where Rena is a lone operator frequently targeted by vengeful rivals, threatened by criminals, and viewed with suspicion by the police. The section’s work involves investigating bogus cases, exposing extortion, and taking down detectives who operate outside the law.

The central narrative arc follows Rena’s quest to identify the mysterious detective who leaked information to her sister’s stalker, a figure she comes to call Shinigami (the Death). Along the way, she clashes with Abiru Yoshinori, a high-profile, media-friendly detective who runs a large agency and uses his reputation to cover up illegal activities. Abiru sees the Anti-Detective Section as a threat and repeatedly attempts to eliminate Rena, leading to a violent confrontation involving a kidnapping, a car chase into the sea, and a final showdown in a burning waste-oil facility.

Another major arc involves a series of disappearances from a domestic-violence shelter, which leads Rena and Kotoha into conflict with a semi-organized criminal group and deeper into the web of the Death detective. The investigation forces Kotoha to choose between her own safety and her loyalty to Rena, and it culminates in a dramatic encounter that reveals the Death’s identity—a figure close to the investigation who manipulated events from behind the scenes. The aftermath leaves Rena emotionally hollow and drifting, while Kotoha continues to train in detective work, eventually becoming embroiled in a new case inside a detention center that ties back to the Death’s mentor.

Throughout the story, the manga emphasizes the gritty, unglamorous reality of the private-detective profession in Japan, contrasting it with the romanticized image in popular media. Rena operates without police backing, often using legally gray methods, and sustains repeated physical and psychological injuries. Her relationship with Kotoha evolves from cold professionalism to a strained partnership marked by trust and sacrifice. The narrative concludes with Rena confronting the true mastermind behind the systematic exploitation of the detective industry, but her personal mission remains unresolved, leaving her to continue her war against corrupt detectives.