In 2015 AD, an unidentified aircraft was observed in the Central Asian region. These flying objects, later called "Dzy" (disaster), had combat power far exceeding that of existing military aircraft, causing significant damage to various locations. To counter them, each country began developing special weapons called "daughters." Two years later, a fleet heading to Japan was attacked by Dzy in Shanghai. During the escape on a lifeboat, the main character, Kei Narutani, witnesses a red fighter shooting at Dzy. Nevertheless, the aircraft is destroyed and falls into the nearby sea. Wanting to help the ejected pilot, Kei ventures alone into the sea and somehow manages to reach the aircraft. Upon reaching the cockpit, he sees not a pilot dressed in equipment, but a fragile and small girl.
