Shiro no Maou to Kuro no Eiyuu

A veteran hero, savior of many worlds, is sent to a new land where orcs and humans are at war. Besieged by the orcs’ superior technology, humanity fights back with magic in a desperate struggle for survival. But the two sides in this conflict are less black and white than they appear, and a hero who has always single-mindedly fought to “save the world” will have to step back and look at his own actions and where they have led him.

(Source: Seven Seas Entertainment)