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.

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.

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.

Kiba becomes entrenched in battle against Karlamine, one of Riser's knights, while Akeno fights Yubelluna, his queen. Meanwhile, Issei takes on Ravel and the other remaining pieces. Rias launches an all-or-nothing sneak attack against Riser.

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!