Nanako is a youthful girl who gains supernatural abilities while simultaneously forgetting her past. A scientific prodigy named Marlow happens to witness the event. Marlow is a diligent student with grand aspirations. He persuades Nanako to join his detective firm by pledging to restore her memories. Nanako naively accepts, yet Marlow"s true motive is to exploit her gifts for his agency and himself. She moves through the city where secrets linger and the shadows of forgotten legends that test her resolve. The plot follows Nanako as she tackles a range of assignments and enigmatic incidents, but her cheerful spirit guides her through each challenge as she solves one puzzle after another.