Issei Hyodo is a second year high school student who has got an enormous sexual addiction and very lascivious behavior. He lives a peaceful life until he is called for a date with a girl named Yuuma. At the conclusion of the date, Hyodo is brought to a local park and Yuuma asks him if he wants to know what her wish is. Under the impression of receiving a kiss from the girl, Hyodo is shocked when Yuuma whispers the words "Can you die for me?" and transforms into a fallen angel. Hyodo is brutally attacked and killed by Yuuma. Hyodo wakes up the next morning believing the events that occurred were all just a dream. Immediately afterwards, he notices Rias Gremory (a third year student at his high school) naked in his room. Rias reveals her identity as a devil to Hyodo and claims that she has reincarnated Hyodo as a devil that serves as an underling to her and the Gremory devil family.