Gantz is a seinen manga written and illustrated by Hiroya Oku. The first issue was published in 2000 in Japan on Shoeisha magazine, Young Jump, and is still in progress at the rate of one chapter every two weeks. In 2004 it was taken out of an anime series of 26 episodes divided into two seasons: Gantz: The First Stage and Gantz: The Second Stage.
plot
Waiting on the subway, Kei Kurono, a young selfish and hypocritical, he sees a homeless man falling on the tracks a few minutes before the train. Carried away by the events he was forced to help his childhood friend Masaru Kato, to save him from certain death. They can aim but are overwhelmed by the arrival of the train. But death does not put an end to their lives: to be found inside an apartment in Tokyo in the company of other people also died just before and a strange black sphere. It is the latter that will deliver a goal: to kill the strange beings within the time limit, since the only way to regain their freedom is to accumulate 100 points ...