In a distant future, most of humanity has been destroyed by extraterrestrial beings called Festum. The survivors wage a brutal struggle against the aliens, who seek to unite all life into a single entity. However, in such a world there is also a peaceful corner—using special shelters, the inhabitants of Tazumia Island try to provide their children with carefree upbringing. But one day this protection also fell, after which the children themselves went to war against the Festum. Long experiments with genetic engineering had made them humanity"s main hope—only they can control the gigantic combat machines called Fafnir.