High school detective Sakuya Outsuki possesses an extraordinary and morbid ability: every time he is murdered, he comes back to life. The son of a legendary detective, he works alongside his capable and devoted assistant, the sixteen-year-old Lilithea, solving cases. However, Sakuya prefers mundane investigations like tracking down lost cats or catching cheating spouses, largely because his unusual talent forces him to experience the pain and fear of death repeatedly.

The series begins when Sakuya takes on a routine assignment to follow a famous movie producer suspected of having an affair. The investigation takes him and Lilithea aboard a luxury cruise ship, where Sakuya quickly stumbles upon the body of a murdered man. As he digs deeper into the mystery, he is killed once again, only to reopen his eyes with his head resting in Lilithea's lap, ready to resume the investigation. The first case introduces other key figures, including Yuriu Haigamine, a young actress involved in the incident, and Sozorogi Kaoruta, a police detective who has known Sakuya for years. The narrative also hints at a larger criminal organization known as the Seven Old Men, with the glamorous and mysterious Shardina Infelicius among its members.

As Sakuya confronts each new case, he is joined by Belka Zeppelin, the assistant to a famous detective from the United Kingdom. The story follows Sakuya as he navigates dangerous mysteries that would be impossible for an ordinary detective to solve, relying on his analytical mind and his strange form of immortality. Each time he dies, he returns to life with the knowledge of his own murder, using that unique perspective to uncover the truth while the ever-present Lilithea remains by his side, welcoming him back from the dead to continue their work. The series blends classic detective fiction homage with supernatural elements, following Sakuya on a path that repeatedly forces him to confront mortality in his relentless pursuit of the truth.