"I want to know all about detectives, but I have no desire to be a detective."

Ever since the day a crooked detective's tip-off led to the murders of her family, Sasaki Rena has been bent on exacting vengeance. With this goal in mind she joins the Detective vs. Detectives Division of the Suma Research Company, whose goal is to crack down on unethical detectives.

Note: Matsuoka started publishing the original novels in 2014, with four volumes total. A spin-off, titled Tantei no Kantei (Detective vs Appraiser), consists of two volumes and concludes the storyline from the main series. He also wrote another two volumes of the original series.

Tantei no Tantei inspired an 11-episode live-action television series in 2015.