This unexpected request from Zenovia puts Issei in a bit of a bind with Rias, Akeno, and Asia. But that's not all; on the day of the public class, strange figures suddenly gather at Kuo Academy, as a conference between angels, demons, and fallen angels is set to take place there soon. Among them is the demon king and older brother of Rias, Sirzechs Lucifer, who, due to a lack of accommodation, ends up at Issei's parents' house.