The anime is about the human race waging war against creatures from Mars. These are large creatures and they attack in huge numbers like ants ganging up on a moth. They invade earth and they want to kill everything moving and eat any tasty humans they see. It’s been twenty years after the first contact between humans and Martians. They’re now at a stale mate. The story follows a group of test pilots developing new weapons to combat these planet invaders. You’d think humans would band together to save Earth but when it comes to dealing with humans, nothing is ever simple.