In the year 2300, humanity has spread and colonized much of the Milky Way, and has even penetrated the Andromeda Galaxy. One of Andromeda's planets, Solo, is explored by a group of archaeologists and soldiers, and they uncover the remnants of a lost civilization: the Ideon, three giant tanks that can transform into a mystical robot; and a powerful starship. Suddenly, the group encounters a landing party from the extraterrestrial Buff Clan, who assume they are being attacked and retaliate; with no alternative to avoid being killed, the group boards the Ideon and defend themselves with it. When Solo's cities are wiped out in an attack, the group takes any survivors aboard the Solo starship and flee into space, taking the Ideon with them as a guardian. And so from a misconception an epic war is born, which takes the crew of the Solo ship through the stars with the Buff Clan in pursuit for possession of the Ideon and its mysterious power source, the Ide.