The Blue World, which symbolizes reason, is under constant attack by the creatures called the Nightfly O'Note originating from the Red World, symbolizing instinct. Akira Asagi, the 17-year-old protagonist who is a researcher at Blue World, is nominated to lead the war at Ryuukyuu LAG, a proud defense facility on the islands of Ishigaki and Iriomote. She meets the sixth combat unit "IS," which was formed four years after a fierce battle that annihilated the fifth unit. Akari must lead these six r...