"Igano Kabamaru" is a martial arts comedy manga set in modern Japan, blending action, humor, and lighthearted drama. The protagonist, Kabamaru Igano, is a young ninja raised in the mountains by his grandfather, a former ninja master. After his grandfather's passing, Kabamaru is sent to live with Mai, a wealthy and eccentric woman who claims to have been his grandfather's lover. Mai becomes his guardian and enrolls him in a prestigious high school, where his ninja skills and naive, carefree personality lead to a series of comedic and action-packed situations.

Kabamaru's arrival at the school disrupts the status quo, as his extraordinary physical abilities and unconventional behavior clash with the school's elite students. His primary rival is Ranmaru Rindou, a skilled martial artist and the leader of the school's kendo club. Ranmaru initially views Kabamaru as a threat but eventually develops a grudging respect for him. The two engage in numerous battles, both physical and comedic, as Kabamaru navigates the challenges of school life while staying true to his ninja roots.

Throughout the series, Kabamaru's ninja training and instincts are frequently put to the test. He faces off against various adversaries, including rival martial artists, delinquents, and even professional assassins. Despite his formidable skills, Kabamaru's lack of social awareness and his insatiable appetite often lead to humorous misunderstandings and mishaps. His relationship with Mai evolves from one of reluctant dependence to genuine affection, as she becomes a maternal figure who supports him in his endeavors.

The manga also explores themes of friendship, loyalty, and self-discovery. Kabamaru forms bonds with several classmates, including the kind-hearted Yukino and the mischievous Kiriko, who help him adapt to his new environment. His interactions with these characters highlight his growth from a solitary mountain dweller to a more socially integrated individual. At the same time, his ninja heritage remains a central aspect of his identity, as he continues to honor his grandfather's teachings while forging his own path.

The narrative balances episodic adventures with an overarching storyline, culminating in a climactic showdown that tests Kabamaru's abilities and resolve. The series maintains a lighthearted tone throughout, with slapstick humor and exaggerated action sequences complementing its more heartfelt moments. The characters' relationships and personal growth are central to the story, providing depth and emotional resonance amidst the comedic and action-oriented elements.