Sensei is a knowledgeable and enigmatic character often encountered in anime stories as a mentor figure to the protagonist. Sensei is often depicted with a calm and collected demeanor, demonstrating an extensive knowledge of arcane subjects that is both admirable and occasionally frustrating to the characters who seek their wisdom. Possessing a quiet strength, Sensei is usually depicted as patient, wise, and cautious, often observing from a distance before acting. A common trait among various Sensei characters is that they may wear a distinctively styled outfit such as a graduation cap or a particular colored overcoat. Relationship-wise, Sensei shares a complex mentor-student bond with the main characters, advising them on their journey, helping them grow and often possessing a mysterious past that gets slowly revealed throughout the series.

Kaiji Itou is the central figure in the gambling anime Kaiji. Driven by debt and desperation, Kaiji exhibits a complex mix of cunning and naivety. He possesses a stubborn determination to win against insurmountable odds, yet struggles with addiction and self-destructive tendencies. He develops a reputation for innovative strategies, becoming notorious for his 'endless eight' technique in Teiai. As a loner, he often clashes with various antagonists but befriends Mikuni and Onizuka, who aid him in his battles. Kaiji's evolution shows him grappling with his demons while maturing through the trials of his high-stakes games.