The story unfolds in the mysterious world of "GANTZ." The protagonist is a high school student named Kei Kurono, who, along with his friend Masaru Kato, dies in an accident while attempting to save someone. However, that is not the end. At the moment of their deaths, they are transported to a mysterious, sealed room. Through the room's window, they can see the Tokyo Tower, yet they cannot leave. Inside this room, they encounter many people who should have died—thugs, attractive women, office workers, politicians, and more. Have they all been reborn? It seems not everything is as it appears. A black sphere in the center of the room suddenly lights up and issues a command. This strange black orb grants them new life, but the price they must pay is to complete missions of killing monsters. Thus, they begin a life of brutal slaughter, fighting for survival on a cruel and deadly battlefield.