One day, a junior high school girl named Iko Kawai encounters an alien and is given a device called the 'Super Income,' which can grant any wish. She also learns about the existence of Martians plotting to invade Earth. To protect the planet, Iko joins the Earth Defense Force 'LTDT,' using the power of the Super Income.

In Earth Defense Girl Iko-chan 2: Lunna's Secret, the mantle of Earth Defense Girl is passed to a new hero after the retirement of Iko Kawai. The new Iko-chan must protect Earth from a new threat, all while navigating the chaos of battling monsters and saving the day.