Simon is a timid boy who has no special abilities except for a knack of drilling underground. Kamina is the polar opposite - reckless and bold and with an incredible sense of self-confidence, he strives to go to a place where there is no ceiling and freedom truly awaits. As they toil in an underground village oppressed by a village chief who disregards anyone who challenges his authority, a gargantuan Gunmen piloted by a Beastman invades the village from the surface. Kamina sees this as his big break to reach the surface. However, what else will he and Simon encounter up there in a world where mankind is under the iron fist of the Beastmen and their Gunmen, led by the mysterious Lord Genome? (thetvdb.com)