"Would you mind dying right now?" are not the words that high school student and lifelong pervert Issei Hyoudou expects to hear from his first girlfriend, especially not before being brutally murdered on their first date. Luckily for Issei, he's saved when he summons the beautiful Rias Gremory, a high-ranking Devil, who reincarnates him as a Devil servant. As Issei learns more about the conflict that has raged between Devils and Angels, he discovers that his "girlfriend" was actually a Fallen Angel named Raynare, sent to destroy him because he possesses a "Sacred Gear," a divine weapon given to humans by the Gods.

Issei is then made a member of the Occult Research Club, the headquarters for the House of Gremory, where he meets the rest of Rias' servants. Given the rank "Pawn," Issei decides that he will rise through the ranks so that he can create his own harem of beautiful girls. However, many grave dangers lie ahead, as Issei must face the Fallen Angels and rogue Exorcists, whilst also trying to master the power of his Sacred Gear.