Kyuu is an ordinary boy with an exceptional talent for logic and reasoning. Eager to become a detective, he learns about the Dan Detective School (DDS), a renowned academy that permits its students to carry firearms. Alongside Megu, a girl with photographic memory; Kinta, a martial‑arts master; Kazuma, a brilliant programmer; and the enigmatic Ryuu, Kyuu confronts a series of meticulously planned crimes, always pursuing the truth.