First appearance: Chapter 268

Oka Hachirou is an almost legendarily skilled Gantzer from the Osaka Team, a veteran of a very large number of games, he was said to have gained a hundred points at least seven times. Oka is a brilliant tactician and hand-to-hand fighter, using all of his equipment to his advantage. He uses his advanced suit's abilities to stay invisible and hidden until he locates the strongest alien among all. Although his equipment is more superior, when he faces an enemy he can´t beat, he has sense enough to retreat without getting his emotions in his way.

His advanced suit includes a build in X-ray scanner, a beam weapon that fires out of its palms, sharp swords protruding out from the back of the elbows, a complete conceal of the body wearer, leaving no point in which a psychic attack may rip someone apart.

The wearer can also unhook their arms from the larger robotic arms so they can use weapons and equipment.

Oka also fights with a mecha, flying monowheel, H-gun, and a normal "Gantz sword".