After quashing the rebellion in Aldegia, Koujou and his friends return to Itogami island to find that in their short absence, there has been a violent upturn in the status quo! The Gigafloat Management Corporation has been hijacked, and war brews between the demon clans for control of the territory. And once again, the Fourth Primogenitor has been drawn into the heart of the conflict, al while the perpetrator's true intentions remain unknown!