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.
Amidst this, a boy named Kawakami Keita, who possesses memories of a "different modern era," successfully bonds with a prototype that no one else could even activate at the military academy he enrolled in. Suddenly dispatched to the battlefield, he utilizes the knowledge from his past life to achieve unprecedented results that overturn conventional wisdom.
—This marked the beginning of humanity's fight to reclaim the world.