In a distant future, a cosmic entity known as the Mother Planet or Mother System, which once maintained harmony across the galaxy, suddenly explodes. From its scattered remnants, 8,888 sentient fragments of its consciousness are born, each manifesting as a young warrior girl known as a Galverse or Gal. The protagonist, Zero, is one of these fragments who awakens on the war-torn planet Amatera with no memory of her past. She crash-lands into the middle of a devastating conflict between a local human resistance and a powerful invading empire known as the Gevuran forces or the Space End Society, an evil organization intent on destruction.

The story follows Zero as she joins Ring, the leader of the resistance, in a desperate fight for survival. Despite having just met him and his people, Zero quickly forms a bond with them, deciding to protect the humans from the robotic invaders. Her actions attract the attention of D.D., another Gal who has sided with the Gevuran empire. D.D. confronts Zero, engaging her in a philosophical battle about whether humanity deserves to exist. As the fight escalates, Zero begins to unlock hidden powers tied to her true cosmic identity, leading to a confrontation that transcends normal space and transports the combatants to a mysterious dimension.

Zero crash-lands on the planet Amatera with amnesia and joins resistance leader Ring. As she fights the Gevuran forces, she encounters other Gals like the antagonistic D.D., who questions why Zero would protect flawed humans. Their battle triggers Zero's latent abilities, revealing that the Gals are connected to a greater cosmic purpose. After a sacrifice that deeply affects Zero, she and D.D. are transported to a white void where they meet other Gal fragments. Through empathy and understanding rather than pure violence, Zero manages to sway D.D. to her side. They return to Amatera and successfully drive back the invaders, learning that all 8,888 Gals across the universe share a mission to restore balance. A post-credits scene hints at a larger conspiracy involving mysterious observers and the true nature of the Mother Planet's destruction.

The main cast includes Zero, a kind yet determined amnesiac voiced by Yui Horie; D.D., a powerful and edgy antagonist turned ally voiced by Fairouz Ai; and Ring, the stoic resistance leader voiced by Mutsumi Tamura. Supporting characters include the cheerful Momo, the young Ran Ran voiced by Ikue Otani, the scientist Dr. Wagami voiced by Kotono Mitsuishi, and the imposing Gevuran enforcer Uvo. The OVA features a stacked voice cast that also includes Akio Otsuka, Yukari Tamura, and Rie Tanaka. The setting is a sci-fi universe blending 90s anime visual motifs with modern themes, characterized by vibrant colors, bold lines, and a distinct gyaru-inspired fashion aesthetic for the female characters. The narrative arc of the OVA episode focuses on Zero's awakening, her immediate conflict with the Gevuran forces, the moral debate between Zero and D.D. over the value of human life, and the establishment of the Gals' overarching quest to heal the galaxy.