Yasuharu Shimaki, known to his teammates as George, is a veteran member of the Osaka Gantz team who first appears during the mission to eliminate the Nurarihyon alien. Before entering the world of Gantz, George worked at a restaurant alongside his close friend and fellow team member, Nobuo Muroya, who is nicknamed Knob. At some point prior to the events of the Osaka mission, George died and was sent to the mysterious Gantz room, where he became a reluctant hunter of alien targets. His success in these missions is demonstrated by the fact that he has accumulated one hundred points on three separate occasions, and each time, he chose to remain in the game rather than being freed from it.

Physically, George is an imposing figure. He is bald, has dark skin, and possesses a large, muscular build that makes him stand out among other hunters. His personality is markedly arrogant and careless, a trait he shares with many of his teammates on the Osaka team. This arrogance extends both to his fellow hunters and to the dangers they face during missions. This callousness is most starkly illustrated through his relationship with Knob. Despite the two appearing to be close friends and coworkers in their civilian lives, George displays a shocking lack of loyalty when they are in combat. When Knob declares he will kill a powerful alien by himself and the fight turns against him, George refuses to help, even as his friend is mortally wounded. This act reveals that George prioritizes the competitive nature of the Gantz game and personal pride over camaraderie.

In the larger narrative of the mission, George serves as a key member of the powerful Osaka team that the Tokyo team encounters. He is portrayed as a highly capable and experienced fighter, primarily using a katana and the powerful Z-Gun. While another member of his team, Yamasaki, claims that George fights like a retard and is the lowest-ranked of the group, his combat record proves otherwise. He single-handedly defeats a boss-level alien worth a high number of points, demonstrating his proficiency with his weapons. After witnessing Knob’s death, George declares that he will kill the remaining boss alien himself, which he succeeds in doing with relative ease despite several close calls. When the final boss, Nurarihyon, arrives, George initially teams up with his teammate Kuwabara to attack it. They cut the creature to pieces, but it immediately reforms and adapts to their attacks. While Kuwabara retreats, believing the monster is too strong and that their leader will handle it, George refuses to give up. In a final desperate act, he grabs hold of the alien, attempting to crush it to death. This plan backfires catastrophically when Nurarihyon transforms into a gigantic colossus composed of naked women, which kills George. His refusal to retreat highlights a core part of his character: despite his arrogance and disloyalty, he possesses an unyielding determination to win the fight on his own terms, even in the face of certain death.