Tempest-King of Mecha

Branded a traitor by the entire league, the "Mech King" Cael Thorne renames himself Ash Gray and hides out as a janitor at a mech academy. When Aria Vale, the woman who once saved him, is betrayed by her fiancé and trapped in a monster death arena, he is forced to awaken Orion Zero, the legendary final mech, and return to the battlefield with 100% neural synchronization.