Heart Gear manga volume 4 features story and art by Tsuyoshi Takaki.

General Wodan has been waiting centuries for the one thing he needs to make his dreams of the ultimate command a reality—a human biosignature. And now that Roue has fallen into his lap, he’s able to rewrite the base program of every gear in Valhalla and force them to fight according to his will. The general has declared war, and Chrome must emerge victorious if he wants to have any hope of saving Roue before it’s too late!