The story describes a woman named Pizuyin who brought a 5-year-old boy to the home of Hiroshi and Misae Nohara and told them that she was the biological mother of Hiroshi and Misae's 5-year-old son Shinnosuke. On the night they stayed, the Nohara family was attacked by a mysterious ninja group. Shinnosuke was kidnapped. Pizuyin's family is the hometown of ninjas, and they have been guarding the energy "Nintoru" of the earth for generations. Therefore, the survival of the earth is handed over to Shinnosuke's ninjutsu.