He was a psychotic yet powerful teenager who participated in the game and won his freedom before the series's events. He desired to return to the game and used a SMG and a pistol to rampage through Shinjuku, killing Hiroto Sakurai, Kenzo Sakata, and Daizaemon Kaze, and either injuring or killing 387 bystanders in broad daylight. He thus not only brought Gantz new participants but also himself because he was killed by Kurono in a standoff. He is an incredible swordsman and was the first to use the Gantz Saber, a katana with a retractable blade that was hidden in one of the apartment's rooms. He can easily be seen as Kei Kurono's "unfeeling" and arrogant rival whose only ambition is to live his life striving to be the best Gantz fighter. He has proved willing to take innocent lives to make it happen (e.g. killing Tae Kojima in one of the missions.) When he earned 100 points for the second time, Izumi chose Option #2 - a strong weapon. Before he can use it, however, he is attacked by a legion of vampires in front of his apartment. After he killed all of them, the four vampire leaders attack him. Izumi managed to kill three of the leaders and was in combat with the blonde vampire before his girlfriend, Ryōko, tried to save him from the blonde vampire. Izumi protected her from the final blow by shielding her with his back. He then marveled at the scores of dead vampires he felled and states that he is definitely going to hell. As of the end of Phase I, Shion Izumi has not been revived.
