Kyuu is a regular guy with a knack for logical reasoning and drawing inferences. He longs to be a detective and by chance, discovers the illustrious Dan Detective School (DDS), a place where students are allowed to carry weapons. Together with his friends Megu, who has a remarkable photographic memory, Kinta, who is a martial arts expert, Kazuma, who is a genius programmer, and the mysterious Ryuu, Kyuu is committed to unraveling intricately planned crimes, always on the lookout for the truth.