Hyodo Issei is a (perverted) high school boy. When he goes out on a date with his first girlfriend Asano Yuma, he is killed by her. Her true identity is Reinare, a fallen angel sent by a secret society Grigori to eliminate dangerous divine weapons. Issei is reincarnated as a devil by his senpai Rias Gremory, a Duke of Hell. Issei serves as Rias's low rank devil and fights against the fallen angels.