The Frontier Lord Begins with Zero Subjects - Tales of Blue Dias and the Onikin Alna

Story:

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.