Issei Hyoudou, a high school student, is your typical pervert who spends his days spying on ladies and fantasizing of having his own harem one day. When a gorgeous girl asks Issei out on a date, things appear to be looking up for him, but she turns out to be a fallen angel who brutally murders him! However, he is given a second shot at life when attractive senior student Rias Gremory, a top-class demon, resurrects him as her servant, enrolling Issei into the school's Occult Research club. Issei must train and battle in order to survive in the brutal realm of angels and devils as he slowly adjusts to his new life. Each new excursion leads to a slew of amusing (and occasionally hysterical) outcomes.