All the perverted Issei wants is to squeeze bountiful boobs all day long, so he's thrilled to join Kuou Academy, a once all-female high school filled with gorgeous girls. But little did the boy know that after finally getting a girlfriend, she'd turn out to be a fallen angel who'd drive a lance through his heart, killing him on the spot! Luckily, the beautiful and busty Rias, his popular classmate who's actually a demon, revives him under one condition: that he'll become her servant. Now, Issei finds himself in the middle of a fierce chess game between demons, fallen angels and exorcists, and the fates of his new friends lie in the balance!