Simon lives a boring life in the underground village of Jeeha, where his main job day in and day out is to dig tunnels. His close friend Kamina, however, longs to bust out of their oppressive existence and reach the surface world where open skies and adventure await! One day, during his usual digs, Simon discovers a robot with a big face buried amongst the rocks. No sooner has he shown Kamina his mysterious find when two beings from the surface crash land into Jeeha Village - one is a gun-toting woman calling herself Yoko and the other is a terrifying mecha piloted by a Beastman! Seeing their chance to escape village drudgery, Kamina rallies Simon and Yoko to defeat the invader using their new robot, Lagann. However, upon breaking out onto the surface world, Simon, Kamina, and Yoko encounter enemies more powerful than they could have envisioned. Their fight for adventure just turned into a war for the survival of the human race - will their lust for freedom hold out against all odds.