Valkyries, the legendary female warriors from the divine realm of Asgard, are dispatched by Odin to safeguard Earth from the escalating demon menace. To counter these threats, nine valkyries, disguised as the Saotome sisters, must strengthen themselves by engaging in various romantic interactions with their designated lover, the Einherjar.
Meanwhile, Takuma Akutsu, a young man plagued by social anxiety, discovers that Odin has selected him to be the valkyries' lover. Despite his deep dismay, he reluctantly allows the sisters to reside in his large but vacant home to assist them in their battle against demons. With nine beautiful women living under one roof, can Takuma conquer his fear of society and rise to become someone capable of saving the world?