You're watching a show that treats 3D mecha like a living, breathing problem to be solved, not just animated. The Gauna aren't villains with motivations you'll understand. They're an extinction event that moves and thinks, and the only thing between humanity and total collapse is a ship that gets smaller and more desperate every episode. The second season stops pretending there's a clean victory waiting.

Having narrowly survived a collision that cost many lives, the ship Sidonia turns from defense to attack, setting course for the Lem system to wipe out the Gauna nest. Captain Kobayashi takes full power and backs the campaign with new long-range anti-Gauna weapons and Tsumugi Shiraui, a human-Gauna hybrid with great destructive power. Ace pilot Nagate Tanikaze is drawn into the expedition, grows close to Tsumugi despite hostility toward such chimeras, and tries to savor the last days of peace with his friend Izana Shinatose as the decisive battle nears. Meanwhile, Kobayashi quietly pursues an experimental weapon that could endanger Sidonia itself. The second season of the mecha sci-fi action series runs for 12 episodes.