Set in the bustling city of Metropolis, a world divided by prejudice and social structures between humans and robots, unrest brews as violence escalates daily. When Japanese detective Shunsaku Ban and his young nephew Kenichi set out to locate the scientist Dr. Laughton, suspected of illicit organ trading, they stumble upon a shocking discovery in the scientist's lab—a girl with no recollection of her past. Determined to aid her, Kenichi flees with the mysterious girl, sparking a chase that delves into the city's darkest secrets. As Shunsaku delves deeper into Metropolis's underbelly to uncover the enigmatic ruler Duke Red, Kenichi races to shield the girl from relentless pursuers. Unbeknownst to them, Duke Red and his heir harbor their own intricate motives for pursuing the girl, tied to her true identity and a power struggle for control over Metropolis.