Daichi Haruka, an ordinary Earth-born boy, journeys to the moon for a summer vacation in 2100, where he crosses paths with V-Mei, a reclusive elderly witch of the persecuted Long-Ears race, and her granddaughter Guri Guri. V-Mei bestows upon him a disc shooter that summons Granzort—a towering Earth-elemental Madou King robot—unveiling his identity as a destined Madou Warrior tasked with defending Rabiluna, the Long-Ears’ homeland, from the invading Jadou Clan.

Honing his command of Granzort, Daichi allies with two fellow Madou Warriors: Gus, wielder of the wind-powered Winzart, and Rabi, master of the aquatic Aquabeat. Together, they clash with the Jadou Clan’s forces across the moon’s terraformed landscapes. The conflict intensifies as the Clan sets sights on Earthly conquest, positioning Daichi’s trio as the last line of defense against interplanetary domination.

The story continues beyond the initial series through expanded OVA continuations, culminating in the 30-minute finale *Non-Stop Rabi*, which expands upon Daichi’s ongoing battles against the Jadou Clan’s escalating threats.

Daichi’s arc centers on his unexpected transformation from tourist to central figure in an extraterrestrial war. His bond with the Long-Ears and capacity to harness Granzort highlight themes of duty and reluctant heroism. His pre-moon life and internal motivations remain anchored to his role as protector, with no documented ties beyond his pivotal relationships with V-Mei and Guri Guri.