Itou Kaiji is a bum who steals car emblems and slashes tires on a regular basis. However, one day, this routine changes when a man in a trench coat pays him a visit. The man reveals himself as Endou, a debt collector, who has come to claim an unpaid loan of 300,000 yen, which Kaiji had previously co-signed with his co-worker, Furuhata Takeshi.

Because of Takeshi’s disappearance, Kaiji is left with an overwhelming balance, but is given the chance to gamble against other bankrupt bums aboard a boat — each gambler is loaned additional money, giving them a chance to pay their dues or become in even deeper debt.Kaiji accepts the challenge in hopes of repaying the compounded debt of 3,850,000 yen and, with luck, winning additional cash…