At the end of the 21st century, a world has been invaded by giant space lifeforms called the Nergal. Reika Minamiya joins the anti-Nergal AG unit to find her older sister who is missing-in-action, but then becomes the pilot of an ancient humanoid robot known as "G's Flame." Along with her fellow recruits, she overcomes her anxieties and turmoil as she comes of age.
