Oku Hiroya to SF Eiga Monogatari : This manga tells stories about the mangaka’s (OKU Hiroya) favorite movies and how they helped and lead to the creation of the manga Gantz.

Kei, a cynical and arrogant high school student, has minimal regard for others; so it’s much to his surprise that when he’s asked by his elementary school friend Kato to save a drunken bum laying on the subway tracks, he actually complies. However, no good deed goes unpunished, and they are swiftly decapitated by the oncoming train. Kei and Kato awaken in a nondescript room occupied by a black sphere and a variety of other people, and thus begins Gantz’s game. In it, the players must face off against aliens in battles where death is inevitable and rewards are minimal. Unfortunately for them, this is just the beginning of their nightmare – at least, for those who manage to survive…