Ōkubo Yorimichi was a player in the real-life game of Btooom! He was in an alliance with Yoshiaki Imagawa and tried to attack Nobutaka Oda's group in the first day, but was incapacitated by him with a Remote Control BIM. Shortly after, Yoshiaki broke the alliance with him and killed him taking his IC chip and his Cracker BIM.
An adult but athletic man, Ōkubo has short black hair. He wears typical salaryman attire: a long-sleeved, buttoned-up shirt; a black coat; a black tie; black pants, with a belt; and black dress shoes. After some time in the island, it seems Ōkubo has left behind his tie and coat. Like all the others Btooom! players, he carries a bandolier and has an IC chip implanted in his left hand.
PersonalityAlthough he seemed scared and dismayed by the situation, he quickly adapted to the game; seen by his collaboration with Yoshiaki in order to hunt other players.
The game has revealed to him that social norms contained him and that his true nature was to be a "hunter", in his own words. He also takes pride in his high school baseball career.