Issei Hyodo's first date with his new girlfriend ends poorly when she turns into a devil 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…

Issei wakes up to find that he is now a devil, and part of Rias' household. He meets the other members of the household, and learns the truth about Yuma. He is called upon to visit a solicitor who has summoned a devil, and secure a devil's pact from him.

Issei meets and befriends a girl named Asia Argento, a Sister who has arrived to serve at the town's church. Issei learns more about the chess game in which he has become a part, and the roles that he and his fellow devils play within it.

Issei is determined to get stronger. He spends some more time with Asia, but once again, their circumstances keep them apart. Issei finds out that although pawns may not be very strong, they have a power that allows them to act like other chess pieces.

While Kiba and Koneko back him up, Issei rushes in to rescue a critically injured Asia. Leaving the others behind, Raynare and Issei become engaged in a duel to the death! Elsewhere, Rias and Akeno have their hands full with Raynare's fallen angels.

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. But it is Rias who appears in Issei's bedroom that night looking to lose her virginity!

Issei begins to train in an isolated area under the watchful eyes of Rias as they prepare for the rating game as Raiser Phenex decides to hold it in ten days.

The time for the start of the Rating Game arrives, and the contestants are transported to a battlefield in an alternate dimension. While Asia and Rias remain at their base, Issei and Koneko face the opposition, and Issei reveals his new signature move.

The Rating Game continue where Rias's Queen is defeat. Issei's Boosted Gear with the help of Kiba's power take out the rest of Raiser's pieces. Rias forfeited to save Issei from Raiser.

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!