On Mars, one of the earth’s colonies has been attacked by the aliens known as Tarsians. In response, the United Nations uses recovered Tarsian technology to make a fleet of starships that will scour the solar system – and beyond – to counter their threat. Mikako, a young student, is recruited to pilot one of the mecha that will be used in combat against the aliens. Though she is eager to help fend off the threat to humanity, she must be separated from Noboru, the one she deeply cares about. They try to retain their relationship throughout the expedition into space, but it becomes clear that distance and time will strain their connection.