Due to an escalating debt, Kaiji Itou is forced to return to his former lifestyle. While strolling on the street one day, he encounters Yuuji Endou, who is pursuing him because of the money owed to the Teiai Group. Unaware of this, Kaiji eagerly follows Endou in hopes of participating in another gambling opportunity. However, his optimism turns into horror when he is kidnapped by the loan sharks.
Since Kaiji cannot repay his substantial debt, the Teiai Group instead sends him to work in an underground labor camp where he must spend 15 years alongside other debtors. His only chance of escaping this torment is by saving enough money to return to the surface for a single day. Once there, he intends to acquire the remaining funds necessary to settle his account through a high-stakes wager. Nevertheless, with numerous temptations threatening his limited income, Kaiji may be compelled to resort to gambling sooner than anticipated.