Odin has tasked the Valkyries, fierce female warriors from Asgard, with protecting Earth from the encroaching demon threat. The Saotome sisters, nine of these divine fighters, must enhance their powers by performing a series of romantic deeds with their official lover, Einherjar. In the meantime, Takuma Akutsu, who is socially anxious, is surprised to learn that he has been chosen as the Valkyries' partner. Despite his overwhelming dread, he opens his spacious but empty home to the sisters to aid them in their battle against the demons. Can Takuma conquer his social phobia and prove himself worthy of saving the world with nine stunning women living under his roof?