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".

Tokyo teens Kei and Masaru are killed by a subway train but awaken in a room with an ominous black orb that gives them weapons, suits and orders. Fighting bizarre alien monstrosities in a deadly game, will they win their freedom or die for the final time? 
(Source: Dark Horse)

Death does not have to be the end; one can live again, but only through beating the game posed by the black ball called Gantz. 
 
On his way home to celebrate his younger brother's birthday, brave and kind-hearted student named Masaru Katou is stabbed to death. He awakes in a small room with a cityscape view in the heart of Tokyo—and he is not alone. To his surprise, it is not the afterlife, but the waiting room for a high stakes game with their lives on the line. Before he has the chance to process the situation, Masaru is handed a gun and teleported into the center of Osaka to carry out one simple task: eliminate any alien on sight. 
 
Accompanied by the aged Yoshikazu Suzuki, the stunning idol Reika Shimohira, and the cold but experienced Jouichirou Nishi, Masaru must overcome his fears in order to survive the game and return home to his waiting brother. 
 
(Source: MAL Rewrite) 
 
Note: A full 3DCG movie adaptation of the manga's Osaka arc.

Birthplace: Osaka Prefecture, Japan
Height: 172 cm
Weight: 77 kg

Kendo Kobayashi is a Japanese comedian.