In a world fighting for its freedom against the alien forces known as the Neuroi, witches—human girls with magical abilities—continue to battle. However, as the persisting conflict affects morale, retired witch and current army member Grace Maitland Steward proposes a unique plan. She believes that the power of music can be an invaluable support that can change the tides of war. Unfortunately, her proposal is dismissed, leading Grace to enlist the help of two successful singing witches, Aila Paivikki Linnamaa and Eleonore Giovanna Gassion. Together, they form the League of Nations Air Force's Music Squadron and recruit seven promising candidates—including 14-year-old Virginia Robertson, who has no military experience but possesses significant abilities.