The world-building is deliberately obscure, you're meant to piece together what the Idaten actually are while watching them get systematically dismantled by enemies they didn't know existed. Peace was a lie the gods told themselves, and the show tears it apart with animators who seem personally invested in making that destruction visceral. By episode three, you understand: there are no good solutions here, only choices that cost something irreplaceable, and the art style keeps you off-balance so you can't retreat into comfortable certainty about who deserves to win.
Eight centuries of peace have made the Idaten complacent. These swift warrior gods were legendary once, celebrated for sealing away demons in a catastrophic war that's now faded into myth. The current generation knows nothing but tranquility, their divine speed and strength rendered irrelevant by centuries of safety. Then the demons return. What begins as a straightforward threat spirals into something far messier. The Idaten must suddenly confront combat they've never trained for, but they're not fighting alone. Human military forces mobilize. Political factions calculate their angles. Intelligence operations unfold in the shadows. Every faction has resources, every faction has an agenda, and nobody plays by yesterday's rules. This isn't a clean battle between good and evil. It's a collision of three powers with competing interests, where violence is just one tool among many. Strategy matters as much as speed. Betrayal lurks around every corner. The Idaten's peaceful existence shatters against a world far more complicated than any myth prepared them for.