Simoun

In the world of Daikuuriku, everyone is born female and selects their desired gender at the age of 17. In this realm, the tranquil theocratic society of Simulacrum is safeguarded by magical flying machines known as "Simoun." These machines can only be operated by young girls who have yet to choose their gender. The Simoun can unleash a magical force called "Ri Maajon," capable of annihilating numerous foes in an instant. When the industrial nation of Argentum decides it must invade Simulacrum to uncover the secret of the Simoun, conflict erupts. This draws the Simoun pilots, known as "Sibyllae" (priestesses who fly the Simoun), into an uneven battle. Due to the ongoing war, the Sibyllae are allowed to defer choosing a permanent gender for as long as they continue flying. Aaeru, a resolute young Sibylla with a mysterious background, and Neviril, the commander of Chor Tempest, Simulacrum's premier Simoun squadron, must guide their fellow priestesses through internal strife and aerial combat. (Source: MU)