Oka Hachirou

Oka is solitary, pragmatic and extremely confident in his abilities. Unlike Osaka veterans who openly compete for points, he avoids wasting effort on weaker enemies and searches for targets worthy of his advanced equipment.

He enjoys Gantz enough to remain involved despite having repeatedly earned opportunities to leave. That enthusiasm does not override his survival instincts: when he concludes that an opponent is too dangerous, he is willing to retreat rather than die for pride.

Oka is also surprisingly casual about his combat background, mentioning online karate lessons and childhood table tennis while demonstrating abilities far beyond those of ordinary fighters.

Oka is an exceptional hand-to-hand fighter and tactician. Seven 100-point clears have given him access to multiple pieces of advanced Gantz technology and extensive experience against powerful aliens.

His Hard Suit is substantially larger and more heavily armored than the standard suit. It incorporates powerful mechanical limbs, concealment, sensors, close-range blades and energy weapons. Oka can disengage his own arms from the larger mechanical arms to use other weapons.

He also possesses a massive Gantz mecha, a flying vehicle and a Z-Gun. Combined with stealth, these allow him to observe a battlefield, identify its strongest enemy and attack with overwhelming force.

Oka is discussed by the Osaka hunters before he appears directly, establishing his reputation long before the Tokyo team sees him. When the mission's major bosses begin overwhelming the other veterans, Oka finally enters the fighting.

He confronts Nurarihyon using his advanced suit and demonstrates combat capabilities far beyond those of ordinary Gantz players. After Nurarihyon repeatedly regenerates and damages the Hard Suit, Oka concludes that the enemy is too dangerous and attempts to withdraw.

Nurarihyon pursues him, and their subsequent battle occurs largely away from the other hunters. The alien eventually returns carrying Oka's severed head, ending the career of the most accomplished known Gantz veteran.

Nurarihyon becomes the opponent who pushes Oka beyond the limits of his accumulated equipment and experience. Oka recognizes that he cannot reliably defeat Nurarihyon and attempts to retreat before the alien hunts him down.

Masaru Katou witnesses Oka's extraordinary fighting ability but is frustrated by the veteran's refusal to continue protecting the remaining hunters once he considers the battle too risky.

Nobuo Muroya, Joji Shimaki, Kazuo Kuwabara and Anzu Yamasaki know Oka as the Osaka team's most accomplished veteran.