The question isn't whether they'll survive the war. It's whether they'll survive choosing who they become. Simoun builds an entire mythology around a single, devastating choice: stay paired forever as women pilots, or transition and lose the only bond that makes you matter. The show moves slowly because it knows that watching someone realize they've been running from themselves hits hardest when you see it coming and can't stop it anyway.

In the peaceful theocracy of Simulicram, every citizen is born female until age seventeen, when each person chooses their permanent sex. But for the priestess pilots of Chor Tempest, that choice remains suspended. Only synchronized Pairs can pilot the Simoun, ancient magical aircraft that protect the nation, and keeping that role means putting off the ceremony for as long as they want to fly. When a devastating assault destroys most of Chor Tempest, the squadron recruits Aer as a replacement pilot. Raw and untested, she faces a daunting challenge: winning the heart of Neviril, the squadron's leader, who still belongs to the Pair she lost in battle during a forbidden Simoun maneuver. As war engulfs Simulicram and rival nations seek the secret of the Simoun, Aer and Neviril must guide their fellow priestesses through conflict both within their own ranks and in the sky.