Itou Kaiji, a down-and-out man surviving on petty theft, has his monotonous life upended when a mysterious trench-coated figure named Endou arrives. Endou, a debt collector, reveals Kaiji's involvement in an unpaid loan he co-signed for a vanished coworker, leading to a staggering debt of 3,850,000 yen. To settle this overwhelming sum, Kaiji is presented with a risky opportunity: board a gambling boat with fellow debtors. On this treacherous voyage, participants must wager borrowed funds, facing either liberation from debt or descending into a cycle of servitude. Reluctantly, Kaiji embarks on this perilous journey, aiming to erase his debt and secure a chance at financial redemption.