Sennen Sensou Aigis: Eiyuu no Kizuna

A long time ago, the deity Aigis imprisoned devils that were causing chaos in the human world. Centuries later, the demon god Tiamat arrives, using these same devils to attack humanity. The imperial capital is among the first to be destroyed. The prince, a descendant of heroes, is forced to flee as his city burns. With his homeland under siege, he must find a way to survive and gather allies to reclaim his kingdom. His fate and the future of his land remain uncertain.