Renton Thurston is a young boy who helps out around his grandfather's mechanic shop; but despite leading a relatively boring life, Renton dreams of traveling the world. However, Renton's life as an average teen comes to a screeching halt when a humanoid mecha called an "LFO" falls down from the sky, only to land right in front of his eyes. From inside the damaged giant, a mysterious girl named Eureka emerges seeking repairs. Renton soon learns that Eureka is a part of the infamous Gekko State, a group of travelers who rebel against the government. He joins them on their travels, but what strange truths about Eureka await him?