In the world of Daikuuriku, all women are born and choose the floor they want to have at the age of 17. In this world, peaceful Srimulakruum's theocracy is protected by magic aircraft called "Symoun", which can be managed only by young people. Girls who have not yet chose the floor. Simoun can activate magic power, known as "Ri Maajon", which can destroy a large number of enemies at the same time. When an industrialized nation Argentum decides that she needs to invade Simulacrum to acquire the secret of Simoun, the war flashes, lubricating Simoun "Sibyllae" (prizes who fly to simoun) in an unequal battle. Since the war is at the peak, Sibylla is given exemption from the choice of permanent sex while they are ready to continue flying. Aaeru, a decisive young Sibile woman with a mysterious past,