Nanako is a cheerful young girl who suddenly acquires supernatural powers while simultaneously losing her memories. The event occurs when a brilliant scientist named Marlow is present. Marlow, a diligent high‑school student with lofty ambitions, persuades Nanako to join his detective agency by promising to help her recover her past. Nanako, trusting him, agrees, unaware that Marlow’s true goal is to exploit her abilities for the agency’s benefit. As the story progresses, Nanako faces a series of perilous missions and mysterious incidents. Her sunny disposition and growing confidence enable her to solve each case one after another.