Kantarō, a five-year-old child, lives with his three-year-old sister An-chan. Their family discovers a mysterious creature named Oochopus after it arrives at their home. Together with his sister, Kantarō welcomes this peculiar lifeform into their household, integrating it as a member of their family. The series portrays their everyday interactions within this adjusted family dynamic, emphasizing the children's evolving connection with Oochopus. Details concerning substantial character development, expanded backstory, or narrative advancement in additional seasons or media beyond the core series remain undocumented. All available information aligns with the foundational premise of Kantarō and An-chan including Oochopus in their familial life.