In a world ravaged by shadowy creatures called the Earless, humanity's champions are the Players, who control mechas known as Equipment to combat these monstrous foes and gain glory and riches. Echo, a young tech enthusiast, aspires to join the ranks of the Players and constructs his own makeshift mecha despite his humble surroundings in the scrap-filled wastelands. Everything changes when he encounters μ (Mu), an amnesiac with a Player's mechanical port, sparking a deep friendship and a shared determination to battle the Earless and protect their world.