Renton, the child of scientists, and Eureka, a girl who cannot endure sunlight, grow up side by side from infancy and bond deeply. One day, Eureka is abducted. Helpless then, Renton swears to bring her back. He enlists in the army and quickly secures a spot in Unit 303 of the First Mobile Forces, thanks to his outstanding display with Nirvash, a biomechanical armor/command system. Unbeknownst to Renton, a scheme exists to halt the ongoing alien assault that involves both him and Eureka within the chaotic conflict, their destinies intertwine as they confront hidden threats together.