After the death of Saizou, Kabamaru's horribly strict grandfather and Iga ninja teacher, an old lady, Ran Ookubo, claims that she received a letter from him asking her to take care of his grandson.

For most of his life, Iga Kagemaru has lived in the mountains with his grandfather, the tough martial arts teacher Seizo Kagemaru. When his grandfather unexpectedly passes away, he is taken in by Seizo's first love, Ran Ookobo, who runs a school in Tokyo. Iga arrives in Tokyo and must deal with living in a town and attending a school for the first time, and all the trials and tribulations it brings - bullies, rivalries, romances and having to deal with an old friend who is reluctantly acting as his foe. Can he manage to survive in Tokyo?—Snake Shadow

An adaptation of the short lived manga series "Igano Kabamaru" (1979-1981) by Yu Azuki. In his youth, the ninja Saizo Igano romanced two rich girls but married another girl. His actions caused a lifelong rivalry between the two girls, and a rivalry between the schools which they operated as educators: Kin'gyoku School and Ogyoku School. Saizo raised his orphan grandson Kagemaru (nicknamed Kabamaru for his insatiable appetite) and the mysterious orphan Hayate Kirino. He trained them both to be excellent ninjas, but otherwise mistreated them and gave them few additional skills. Following Saizo's death, the legal custody of Kabamaru passes to Saizo's former lover Ran Ookubo. Kabamaru moves to Tokyo with her, and gets caught up in the intense rivalry between the two schools. There is mutual attraction between Kabamaru and his legal guardian's orphaned granddaughter Mai Ookubo. This is complicated because Mai finds Kabamaru's coarse manners to be a turn off. Kabamaru is further frustrated because his surrogate brother Hayate has apparently turned against him and acts as his enemy.—Dimos I