In a distant era of legends, the kingdom of Mu faces the relentless onslaught of the Dragonian Empire led by the formidable Dorado, the Golden King, with only a deity's statue to guard them. Queen Aira, seeking salvation, calls upon a warrior from a different time and world – Yamato Hino, an ordinary yet athletic high school student in modern Tokyo. Initially skeptical of the spectral messages from a mysterious young woman, Yamato is drawn into a mystical portal transporting him to ancient Mu. As Dragonia launches another assault, Yamato merges with the colossal God Mazinger, turning the tide of battle. Despite this initial triumph, both Mu and Yamato must traverse a path of growth and self-discovery. Yamato must conquer his inner demons to become the hero that Mu desperately needs and find his way back home.