Kyokutou Kyuseishu Densetsu Shounen, Igyou no Kitai de Musou Suru

When the boy pilots that bizarre mech, the battle for humanity to reclaim the world begins.

Due to a ritual of demon summoning conducted at the end of World War II, the state of the world changed drastically. A hundred years later, humanity has been resisting the demons, who have become the rulers of the world, by creating magical mechs...