Ryoumin 0-nin Start no Henkyou Ryoushusama

Dias fulfilled his parents' will to help others, and kept fighting on the battlefield to that end. Now known as the "Savior Hero" from his long wartime career, he was rewarded with a vast territory from the king. After having met the horned Kijin (鬼人) girl Aruna who lives there, he begins his new slow life as a lord, seeking to thrive in spite of increasingly realizing that he was rewarded with the short end of the stick.