Beset by an unprecedented wave of monsters, the group of small to medium-sized countries known as the Union of Eastern Nations is in dire straights. Requested to send reinforcements 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 retainers' strength to save Lastania...