The main character of the story. Kaiji is poor, downtrodden and lazy—he lives by himself in a slum and is constantly in debt. He bides his time by playing cheap gambling games with neighbors, though he always loses. In spite of this, when his life is in danger, he displays a remarkable hidden capacity for gambling, which allows him to endure the hardships he faces. He is shouldered with a 3,850,000 yen debt at the beginning of the story by a coworker who convinced him into co-signing a loan, leaving Kaiji with the full weight of the debt compounded over a year.