From Aku Tenshi:

The world of Waq Waq is a place where machines attack the black-blooded humans, whose only defense are the Sakimori, humans chosen to partner up with the Goujin-zou, a race of machines that grow stronger when melded to humans. Shio and his Sakimori father, Al, upon entering a village, are attacked by the machines. As Al falls in battle, he leaves his son to become the new Sakimori and guardian of a mysterious young girl, believed to be god, found at the heart of the battle. Waq Waq is the story of Shio as he battles to protect what was entrusted to him by his father. Let the battle for God begin!