After one of his coworkers fails to repay a debt, apathetic bum Kaiji Itou is pressured by loan sharks to settle the large sum of cash. Since Kaiji has little money and no future prospects of his own, he is unable to return what his colleague borrowed. Faced with massive financial burdens, Kaiji is given an offer to board the illustrious Espoir—it is said that "one night aboard the ship, and all of your debts will be paid."

What seems like a simple night of gambling quickly turns into a game of strategy and betrayal. With the losers of the tournament being subjected to a backbreaking life of indebted servitude, Kaiji must choose his actions—and allies—carefully. However, this is only the beginning of a series of gambles that will wager Kaiji's life, testing the full extent of his wits and will to survive.