Beset by an unprecedented wave of monsters, the group of small to medium-sized countries known as the union of Easter Nations is in dire straits. Requested to send reinforcement to their aid, Souma dispatches troops to the kingdom of Lastania-where Julius, former crown prince of the principality of Amidonia, is currently holding the monsters at bay. And so it comes to be that Souma, standing shoulder-to-shoulder with an old foe, must depend on his retainer’s strength to save Lastania.