Ossan, Yuusha to Maou wo Hirou @comic

An old man is forced to retire from the adventurer's guild and decides to return to his hometown. On his way, he picks up two babies. The first one is a human baby with the emblem of a hero. The second was a baby of the demon tribe with the emblem of the demon king. And so the story of the old man who picked up the hero and the demon king begins.

(Source: MU)