When Kaiji is told there have only been two winners of the Bog, Hyōdō and Tonegawa, he realizes that the game must be rigged. He then agrees to work with Sakazaki for 10% of the possible ¥600 million payout from the Bog, however Sakazaki is secretive about the details of his plan which includes the machine's maintenance schedule. A day before their attempt to beat the Bog, Sakazaki appears with ¥50 million he 'borrowed' from the company president's safe where he works as a security guard. At the appointed day, Sakazaki commences to play the Bog.
坂崎に連れられ入った裏カジノ。カイジがそこで出会ったのは、帝愛の息のかかった究極のモンスターマシーン…1玉4000円のパチンコ、『沼』!! １日で6億という一攫千金目指し、坂崎の策に乗り協力者となる。 そして決行の日！『沼』攻略の秘策を手に坂崎と共にカイジ、いざ勝負!!
사카자키의 권유로 들어간 불법 카지노에서 만난 것은 구슬 하나에 4천 엔의 슬롯머신 '늪'이었다. 당첨만 되면 6억을 벌 수 있는 일확천금의 기회를 노리며, 사카자키의 계획에 협력하게 된 카이지. 늪 공략을 위한 비책을 준비한 사카자키와 카이지. 그들과 늪의 승부가 시작된다.
开司身负拯救四五组的所有人的使命回到地面上，在东京四处寻找赚大钱的方法，结果遇到了坂崎，在坂崎的带领到来到了一间地下赌场，见到了一台一颗珠子四千日币，开奖可以赚到五六亿的怪物钢珠台。并决定与坂崎联手攻陷这台怪物。坂崎答应事成後给开司中奖金额的10%，也就是六千万做为报酬，开司是否能顺利赢得六千万呢？
