Choujuushin Gravion is a mecha anime series that follows the story of Eiji Shigure, who infiltrates the mysterious Klein Sandman’s castle to find his missing sister. He discovers the powerful robot Gravion, built to protect Earth from the alien Zeravire threat. Eiji, along with other pilots, must work together to control Gravion and defend the planet. The series blends action, adventure, and science fiction themes.