Timid but kind-hearted office worker Saneshige Yoshisu is heartbroken when his best friend, whom he secretly had a crush on for years, got married. Seeking solace from a cat living at a shrine, he suddenly gets caught up in a scuffle between a gigantic cat and a man in a strange Japanese costume, and ends up on the verge of death. Saneshige awakens to find himself in a world inhabited by inhuman beings, and learns the man who saved him is the leader of demons - who declares Saneshige is now his wife!