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.

Summer break is coming up fast for Hyodo Issei, but all his plans are put on hold when he finds out he is to accompany Rias for her visit back home to the underworld! A new adventure is about to begin and all the while Koneko is not acting herself.