Sebastian

Sebastian is calm, cryptic and unsettlingly detached. He answers questions indirectly and seems more interested in observing Kikuchi's reaction to the truth than in providing a straightforward explanation.

His deadpan demeanor persists even when discussing extraordinary subjects. Rather than attempting to reassure Kikuchi, Sebastian deliberately pushes him toward increasingly disturbing possibilities about Gantz, humanity and reality itself.

He also displays a cruelly playful streak. Once his true capabilities become apparent, he treats catastrophic events as demonstrations intended to make a philosophical point.

Sebastian initially appears to possess no unusual abilities, functioning simply as Kikuchi's German interpreter and guide.

He later demonstrates powers vastly beyond human capability. Sebastian predicts and apparently causes the sudden death of an elderly woman, creates a fatal automobile accident and brings down an aircraft as demonstrations for Kikuchi. He then disappears through a transfer effect resembling Gantz teleportation.

The exact nature and limits of Sebastian's abilities are never fully explained. His actions imply control over events on a scale that makes ordinary Gantz technology appear comparatively limited.

Sebastian enters during Kikuchi's investigation into the origins of the black spheres. He takes Kikuchi to the German factory producing Gantz technology and subsequently introduces him to Heinz Bernstein, allowing the reporter to hear an explanation of how the manufacturing operation began.

His role changes after that meeting. Sebastian draws Kikuchi back out and challenges the explanation Bernstein provided, stating that Bernstein's daughter merely received information rather than inventing it. He raises ideas involving the Akashic records, simulated reality and God taking human form.

His final demonstration leaves Kikuchi confronted with a being whose apparent power cannot be explained by the human organization manufacturing the Gantz spheres. Sebastian's precise identity is deliberately left unresolved.

Seiichi Kikuchi is the journalist Sebastian guides through the German side of the Gantz investigation. Sebastian eventually reveals his extraordinary abilities directly to Kikuchi, using several deaths and disasters to challenge the reporter's understanding of reality.

Heinz Bernstein is the industrialist Sebastian introduces to Kikuchi. Sebastian later disputes the idea that Bernstein's family originated the information behind Gantz technology.