Takuma Akutsu is a withdrawn, fearsome-looking high schooler who is suddenly chosen by the Norse god Odin to help save the world from invading evil deities. Odin sends his nine Valkyrie daughters, the Saotome sisters, to live with Takuma, and their combat strength grows stronger the closer their bonds with him become. Caught between everyday school life and apocalyptic battles, Takuma must embrace the role of their reluctant lover and protector as the fight escalates.