One year after clearing his debts and escaping the clutches of the Teiai Group, Kaiji Itō finds himself once again trapped in a cycle of poverty and despair. Reduced to scraping by on meager earnings, his situation takes a catastrophic turn when he is kidnapped and forced into a brutal underground labor camp to work off a massive new debt. Inside this hellish facility, the currency is "perica," and the only hope of buying a day on the surface is to hoard enough of it. After witnessing the endless suffering around him, Kaiji risks everything in a dice game against the sadistic foreman. Against all odds, he wins a chance to return to the surface for two weeks, carrying one million yen and a desperate promise to the other laborers: he will find a way to earn the 200 million yen needed to buy their collective freedom.

With only fourteen days to achieve the impossible, Kaiji reunites with his former nemesis, Yukio Tonegawa, who has also fallen from grace. Tonegawa reveals the existence of "The Swamp," a monstrous, transparent pachinko machine hidden in an illegal casino. The machine is a marvel of manipulation, designed by the cold and calculating prodigy Seiya Ichijō, and offers a top payout of one billion yen. To beat it, Kaiji forms an unlikely alliance with the experienced gambler Kōtarō Sakazaki and the determined Hiromi Ishida, the daughter of a man who once helped Kaiji. Their fight against The Swamp is a grueling psychological war, where each pachinko ball fired is a bet against the house's meticulously rigged odds. They must navigate a series of treacherous side games, including a life-or-death choice-based game called "The Princess and the Slave," which tests the very limits of their trust and loyalty as betrayals and shifting alliances threaten to destroy them from within. In a final, desperate gambit, Kaiji must confront Ichijō directly, risking everything not just for the money, but to shatter the system that preys on the hopeless.