Since the arrival of D2s, an invasive species originating from a black meteorite that crashed to Earth, the United States of America has been in disarray. To prevent more tragedies caused by the D2s' disdain for music, a governmental edict prohibited residents from playing any melodies—this restriction is still in place today, in 2047. Musicarts, young ladies who symbolize pieces of classical music, and Conductors, who manage them, are humanity's sole line of defense against the D2s. Takt Asahina, an aloof piano prodigy, is converted into a Conductor after a random D2 strike. The same occurrence kills Anna Schneider's younger sister, Cosette, and introduces Takt to his Musicart, Destiny. Takt is looking for a way to keep their agreement together.