Issei Hyodo's first date with his new girlfriend ends poorly when she turns into a monster and stabs him in the stomach. Luckily, he's saved by Rias, the buxom president of his school's Occult Research Club. And then, things really start to get weird...

Surprise! All the members of the Occult Research Club are devils, including new-recruit Issei, who's having difficulties figuring out the whole "demonic power" thing. Maybe he'd have better luck if Fallen Angels stopped popping up and trying to kill him.

New living arrangements are made for Asia, who has been living in the club's room. Meanwhile, Issei begins a new training regimen with Rias to improve his physical fitness. Asia begins attending school, where she is placed in Issei's class.

Rias decides that it is time for Issei and Asia to have servant familiars. The school's student council visits the club room, and Issei learns that they are another faction of devils. The two groups compete to see who gets first pick of the new familiars.

Issei dreams that he is marrying Rias, which leads him to get in touch with his inner dragon. Asia confesses a desire to have a deeper relationship with Issei.

Issei wakes up to find that the battle is over, and he has lost. Rias and the others are at a party in honor of her engagement to Riser, but with some help from Grayfia and Asia, Issei decides to crash it, rescue Rias, and bring her home with him!