Humanity has journeyed to the stars and encountered various alien civilizations, now long extinct. After uncovering the archaeological ruins of such a civilization on the planet Solo, humans finally experience their first contact with a living alien race: the Buff Clan. When Karala Ajiba, daughter of the Buff Clan's military commander, steps onto Solo's surface, the Buff Clan initiates a savage attack on the colony to reclaim her. To escape, Cosmo Yuki, Kasha Imhof, and Bes Jordan board three trucks that quickly transform into the giant humanoid robot Ideon. Following the destruction of the Solo settlement, the survivors take refuge on a recently unearthed spacecraft—the Solo Ship—and flee, striving to distance themselves from the aliens and ultimately find peace. The relentless Buff Clan, however, remains in close pursuit and refuses to yield so easily.