Kurosaki intervenes and tells Ōtsuki that he has no choice but to play, and in the end, he loses 18,252,000 perica which Kaiji splits equally between the Forty-fivers. Kaiji then asks Kurosaki to approve their requests for the one-day outside pass and he agrees. The Forty-fivers insist that Kaiji should keep the money and twenty one-day outside passes, leaving him with ¥800,000 (around US$7,800) to gamble for the team and pay off their debts. Now back in society above ground, Kaiji meets Sakazaki Kōtarō who is looking for a partner to win big in the illegal casinos. Kaiji accepts his offer, and is taken to an illegal casino where he sees a huge Pachinko machine called "The Bog". Each ball is worth 1,000 times more than normal and the jackpot is worth ¥550 million, more than enough to free Kaiji from debt.

Sakazaki starts to play the Bog, using an initial ¥10 million, dropping balls onto the final holed plate, but they do not have enough momentum. During the game Kaiji successfully passes Sakazaki his pre-prepared magnetized beer can and he prepares to use it to increase the centrifugal force of a ball to make it drop through the winning hole. However the effect is insignificant, but Sakazaki continues, wagering another ¥10 million. Kaiji overhears the security men talk of a device to prevent anyone winning and Kaiji warns Sakazaki's to stop, but he is in a gambling frenzy and continues to play using the money he 'borrowed' from the company safe.

Sakazaki ignores Kaiji's warning and continues sinking money into the Bog, while the casino manager gives instructions to initiate the 'block' which controls the flippers, stopping the balls descending into the winning zone. Although Sakazaki is close to winning he collapses and the casino manager, Ichijō Seiya, introduces himself and reveals that they are using brass balls today which are not affected by magnetism. They leave with a little more than ¥6 million after losing over ¥43 million in two hours. The next day, Kaiji spends hours back at the casino, staring at the machine, then goes to the staff room to cash in one ball he found, insulting Ichijō but also gathering information about the casino's operations.

Sakazaki enters the casino to challenge the Bog again, dressed as a Komusō monk. He plays the machine, quickly losing his stake of ¥6 million, then attacks and damages it. Ichijō is suspicious of his behavior and realizes that it is a distraction and rushes to his office to find Kaiji there. Ichijō has Sakazaki beaten up and Kaiji tortured, then they are thrown out into the street. Days later, the Bog is repaired and operational again. It is Kaiji's final day on the surface and he arrives at the casino to challenge the unbeatable Pachinko machine.

On Kaiji's last day above ground, he challenges the Bog and Kurosaki warns Ichijō that Kaiji must have a plan, and Ichijō's reputation is on the line. Kaiji starts playing and more balls than expected drop between the pins and Ichijō is suspicious. It takes him some time to realize that Kaiji somehow entered the staff room and doctored the setting gauges for adjusting the pins so they were set wider apart. Panicking, Ichijō has the 'block' turned on, directing the balls away from the winning path.

Kaiji's improbable idea of tilting the building to tilt the Bog pays off, and he gets closer to winning with more balls dropping onto the third and final plate. Ichijō contemplates the consequences of losing everything he has and tilts the machine again in the same direction to prevent balls reaching the third plate as Kaiji uses his last ¥10 million.

Kaiji commences to play with the last ¥10 million he borrowed from Endō for a final assault, unaware that Ichijō has tilted the machine in the same direction that Kaiji's group tilted the building, thus creating an almost insurmountable tilt on the first two plates. When half of the money is gone, Ichijō gloats to Kaiji that he can never win, but Kaiji says that he knows about the tilt. As the crowd watches, Kaiji tapes three ¥10,000 bills to the glass, hiding the three plates. In frustration, Ichijō rips them off to see a number of balls circulating on the plates because the losing holes have become clogged with balls which are unable to exit the machine. This increases Kaiji's probability of winning, however they still do not drop into the winning hole.

Kaiji continues to play until the losing holes on even the third plate are blocked; however, Ichijō has the final weapon – air jets around the winning hole to deflect the balls. In the hushed silence, Kaiji hears the sound of hissing air and deduces what Ichijō has done. As Kaiji runs out of balls to play, the Teiai security men in black arrive to take him back underground. Kaiji proposes calling it a draw to Ichijō who refuses, forcing Kaiji to play his remaining balls and pray for a miracle.

Even with the plates filled to the brim with silver balls, Ichijō's secret weapon, the Curtain of Wind, prevents Kaiji from winning and Kaiji has run out of money. As he is dragged away, Sakazaki appears swearing vengeance on the machine, and gives Kaiji another ¥10 million which he again 'borrowed' from the company safe. Kaiji starts playing again with renewed vigor. The bottom plate is now awash with balls, but none can pass the curtain of wind around the winning hole. The machine appears to groan, and with the plate overflowing with balls, some cascade down the winning hole. Horrified that Kaiji won, Hyōdō sentences Ichijō to 1,050 years underground.