After Kei and his childhood friend Kato are torn into bloody pieces by a speeding train, they awake in an unfamiliar room surrounded by strangers. In the middle of the room is a bizarre black sphere: the Gantz.
The scores are tallied and Nishi explains some of what he knows about the rules of the strange world of the Gantz. The unusual situation grows even odder the next day when Kei wakes and finds that this nightmare is no dream.
Kei, suitless and outnumbered by the Suzuki aliens, must face the biggest monster alone. When the battle ends and the scores are tallied, the group sees that there might be a way to escape their strange fate.
The team's efforts to defeat the giant aliens are hindered by two thugs who are brutally tormenting a homeless man—and he just happens to be the same guy that Kei and Kato encountered just before their deaths.
Change is in the air for the players of the deadly game. Fed up with his aunt, Kato finds a new place to live with his little brother. Meanwhile, Kei's attitude pushes Kishimoto away; and Tetsu's life spirals brutally out of control.
The new players are beginning to realize that the bum-killing freaks are really dangerous. As the situation escalates, the members of the team look to Kei—the one person who might be able to help them survive.
A new round begins for the gang. Appearing before the Gantz, they find themselves joined by a diverse group of fresh players. As the game gets underway, Kei panics when he realizes his suit is nowhere to be found.
As the group prepare to track down the Suzuki alien, Tetsu's gang are creating conflict and Nishi's smart mouth isn't helping the situation. When tensions boil over, blood is spilled before the hunt even begins.
Kato is forced to take action to save Nishi from certain death, but he may not be ruthless enough to kill the Suzuki alien. Time is running out for yet another player trapped in the cruel world of the Gantz.
The carnage continues and truly no one is safe. As wounded Kei struggles to stay alive, his teammates fall one after the other. When the final foe is defeated, only one player will be around to see the score.
With the small alien dead, the large alien exacts its revenge, slaughtering many with the group. When the creature pursues Kei, the young man quickly discovers that his physical abilities are enhanced by the suit he wears.
The Gantz calls the players for another round. Among the new faces gathered before the sphere: a television evangelist that thinks he has all the answers and a girl who seems willing to give Kei the attention he seeks.
When Kato shares what he knows in an effort to help the new players, the evangelist begins to think something sinister is afoot. The holy man learns just how correct he is as the game's new targets make their presence known.