Mao-Chan is a 2nd grader whose grandfather is the Chief of Staff of the Ground Defense Force. She has been trained to become a valuable member of the force since she was born. When she turns eight, she, together with her friends Misora and Sylvia, form the elementary school self-defense team. Mao protects the land, Misora, the skies, and Sylvia, the sea. These pint-size girls do their best to protect Japan from "cute" alien invaders.