Kagemaru, orphaned young, was raised by his grandfather Saizō Igano in the mountains of Iga Province. Saizō subjected him and fellow orphan Hayate Kirino to grueling ninja training. Kagemaru's prominent front teeth and voracious appetite earned him the nickname "Kabamaru," meaning "hippo's mouth." Training included food deprivation as motivation, forging exceptional physical abilities: superhuman speed reaching 100 km/h, strength enabling jumps over 200-meter skyscrapers, cat-like reflexes, and iron-like legs.

Anime adaptations depict him with dark skin, contrasting his lighter-skinned manga portrayal. He frequently wears a fishnet shirt. After Saizō's death, Ran Ookubo arranges his move to Tokyo, causing severe culture shock. His rural upbringing leaves him unfamiliar with urban customs, modern etiquette, and formal education, resulting in poor academics and limited literacy.

His personality blends naivety, impulsiveness, and a carefree spirit. He acts without forethought, charging into situations, yet possesses innate kindness. An enormous appetite—especially for yakisoba and fried shrimp—drives much of his behavior. In Tokyo, he develops instant romantic feelings for Ran's granddaughter Mai Ookubo, though she initially recoils at his crude manners and animalistic eating habits.

Relationships shape his growth. His bond with Hayate evolves from shared traumatic training to estrangement, culminating in a forced duel resolving their conflicts and leading to reconciliation. With Mai, mutual annoyance shifts to romance after he protects her in a blizzard, revealing his caring nature. This pivotal moment and his later commitment to resume ninja training while honoring promises to Mai demonstrate maturity.

A sequel manga, "Igano Kabamaru Sorikara," introduces his son (Ko)-Kabamaru Igano, implying marriage to Mai. Saizō is later revealed to have faked his death; Kagemaru ultimately returns to Iga with Hayate to continue ninja training.