Since the birth of D2s, an invading 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 public edict was issued prohibiting 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 govern them, are humanity's sole defense against the D2s.