The chapters of the Japanese manga Gantz are written and illustrated by Hiroya Oku, and have been published in the Japanese manga anthology Weekly Young Jump since its issue 32 published in 2000. The plot follows a teenager named Kei Kurono and his friend Masaru Kato who die in a train accident and become part of a semi-posthumous game in which they, and several other recently deceased people, are forced to hunt down and kill aliens. Gantz is divided into three main story arcs referred to as "phases". After the completion of Phase 1, the author put the series on hiatus for a short time to work on Phase 2, which is also known as "Catastrophe". Phase 1 consists of the first 237 chapters. On November 22, 2006, the first chapter of Phase 2, chapter 238, was released. As of chapter 303, the series was put in hiatus once again in order to let Oku prepare in the making of the final arc of the series. The series continued serialization in October from 2009. The individual chapters are collected by Shueisha in tankōbon format; the first volume was released on December 11, 2000. 37 volumes have been released by Shueisha. An anime adaptation, produced by Gonzo and directed by Ichiro Itano, aired in Japan on Fuji Television and AT-X.