Daichi Haruka, an 11-year-old Earth-born tourist, journeys to the moon in 2100 to investigate rumors of rabbit-eared beings. This quest leads him to the Long-Ears tribe members V-Mei and Guri Guri, unveiling his destiny as Earth's chosen Madou Warrior. Endowed with potent Madou Force, he wields a disc shooter to summon and pilot the Earth-elemental Madou King Granzort.

Commanding Granzort with earth and fire powers, Daichi employs the colossal Erdy Kaiser sword for decisive strikes. His self-built rocket-powered jet-board aids mobility and facilitates Granzort's summoning. Personality-wise, he blends inventive curiosity with leadership instincts but harbors a severe carrot phobia—overcome only in the finale by consuming a carrot slice.

Traveling to Rabiluna, he forges a trio with fellow warriors Gus Yamamoto and Rabi, confronting zones tainted by the Jadou Clan's dark magic. Setbacks test his resolve: Granzort's incapacitation in battles (episodes 23 and 38) and the theft of his father's music box memento during Rabi's capture. Family ties deepen through the music box subplot, symbolizing paternal absence. His mother's appearance at Rabiluna's Luna Core climax aids his emotional reconciliation and role acceptance. Loyalty is further challenged by the revelation of Rabi's grandfather, Lord Agramant, as a corrupted Long-Ear.

For the OVA "Bōken-hen," no concrete details regarding his role or development are available.