Perverted youth Issei Hyoudou's dreams seem to come true when the beautiful Yuuma Amano asks him out on a date. But when she reveals her identity as a fallen angel and tries to kill Issei, his death seems imminent—until an upperclassman named Rias Gremory rescues him. When he wakes up again, she reveals herself to be a devil. In order to save Issei, she reincarnated him as one of her kind, making him her new servant.

This turn of events thrusts Issei into the world of the supernatural. As he is introduced to the various devils in the Occult Research Club at his high school, he must learn to adapt to this new world filled with devils and fallen angels. Setting his sights on becoming powerful, he must decide what is truly important to him as he comes to realize that the life of a devil is not an easy one.