Our War That Ends The World, Or Perhaps The Crusade That Starts It Anew

A brief description of the Our War That Ends The World, Or Perhaps The Crusade That Starts It Anew manga: 

The Empire is a nation of advanced technology. The Nebulis Royal Family Agency is a land that is feared as a “witch’s land”. In the midst of an endless war between them two boys and a girl met on the battlefield. The icy witch is revered as the strongest in the kingdom and the young swordsman, who is one of the greatest forces of the Empire.