Zeravire, a new threat, launched an attack on the solar system in 2041 AD. The devastating attacks brought down military bases, leaving the citizens of the galaxy feeling hopeless. But Klein Sandman, a billionaire who had anticipated the invasion, set up a defense mechanism quietly. His secret weapon was Gravion, an enormous robot that utilized gravity power. Meanwhile, a young man named Eiji infiltrated Sandman's facility to look for his missing sister. There he met Toga, another young man. The duo teamed up with four other brave individuals and ventured into battle aboard Gravion to eliminate the Zeravire peril.