It tells the story of Kei Kurono and Masaru Kato, both of whom died 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 armed with a handful of futuristic items, equipment, and weaponry.

A pair of high school students, Kei Kurono and Masaru Kato, are hit by a subway train in an attempt to save the life of a drunk homeless man who had fallen onto the tracks.

Following their deaths, Kurono and Kato find themselves transported to the interior of an unfurnished Tokyo apartment, where they meet Joichiro Nishi, a Gantz veteran, and other clueless participants.

After some time in the room, the Gantz sphere opens up, revealing a bald naked man with a breathing mask and wires attached to his head, and various weapons for them to use.

These include the custom fitting black suits which give them super-human strength, speed, stamina and damage resistance, a controller which acts as a radar and stealth unit, X-gun, X-Shotgun, Y-Gun.

When the Gantz sphere opens, green text appears on its surface, informing those present that their "lives have ended and now belong to him".

In a desperate attempt to revive his best friend, Kato fights the one hundred point alien Nurarihyon which obliterates both Osaka and Kurono's team.

At the end of the mission, similar to the first time Kato died, he defeats arguably the strongest alien in the series and is laid bleeding on the floor.

The series depicts both the missions and Kurono's regular life, as well as the daily lives of other Gantz players (to a lesser extent).

At the end of that week, a massive alien force invades the Earth and begins exterminating the human race, while Kurono and his companions try their best to make use of Gantz' advanced technology and weaponry in defense.

Nishi, in the chapter "The Great Escape", is left for dead by Kurono, vowing vengeance against him and crying out for Gantz and mother for help.

Prior to this announcement Eeva completely dominates all Gantz teams in his vicinity by killing all the hunters, giving the human race a sense of their mortality.

However, he did not decide to make Gantz until after writing the manga Zero One; Zero One had a similar setting, but Oku ended the series, noting it was not very entertaining and that it was too expensive to develop.

Once done, Oku prints the characters and backgrounds he made in 3D, adds tone and color to the pages, and finishes with sound effects and dialogue.

[6] Some plot twists are meant to go against common events that happen in several manga such as the deaths of the major characters like Kei Kishimoto and Masaru Kato.

[4] Gantz, written and illustrated by Hiroya Oku, debuted in Shueisha's seinen manga magazine Weekly Young Jump on June 29, 2000.

[15] In North America, publishing company Dark Horse Comics acquired the licensing rights for the release of English translations of Gantz on July 1, 2007, during the Anime Expo.

[21] Gantz/Osaka, showing the stories of the Gantz Osaka team, has been published in Japan in 2010 and compiled in 3 volumes released by Shueisha between October 20 and December 17, 2010.

[22][23] A special chapter Gantz no Moto that has Hiroya Oku telling the story on how he got into the manga business and what films influenced him was published in Miracle Jump on January 13, 2011.

[34][35][b] The first stage aired on Fuji TV with several scenes censored, due to content that were deemed inappropriate, such as violence or nudity.

[50] It takes place before the events of the manga, with the focus being on the characters Shion Izumi and Joichiro Nishi, who participate in Gantz's missions.

[51] Another novel, titled Gantz/EXA, planned by Yumeaki Hirayama, written by Junjo Shindo and illustrated by Koji Ogata, began serialization in Weekly Young Jump on September 16, 2010.

The films star Kazunari Ninomiya and Kenichi Matsuyama in the roles of Kurono and Kato respectively, and were directed by Shinsuke Sato.

[55] At the end of this special Los Angeles showing, which took place at the Mann's Chinese 6 theatre, there was a discussion and live interview with both the male leads,[56] as well as a teaser trailer for the second installment, Gantz: Perfect Answer, which was released in Japan on April 23, 2011.