Gantz tells the story of a teenager named Kei Kurono who dies in a train accident and becomes part of a semi-posthumous "game" in which he and several other recently deceased people are forced to hunt down and kill aliens. The missions on which they embark are often dangerous. Many die - again - on each mission, but they are replaced by others in the same manner as Kei Kurono's appearance.
Kei Kurono often faces many hard times and difficult experience to choose his own decision to save his life and his friends and hence, through many tasks of many destination in the vast worldwide. The mission made strong and tough relationships between the core member of 'Tokyo' team.