Ryoumin 0-nin Start no Henkyou Ryoushu-sama

Dias returns from decades of war as a celebrated hero and is rewarded with a domain of his own. The problem is that his new territory is little more than open grassland with no town, no home, and not a single subject. For a man who knows how to win battles but nothing about farming or government, starting from a population of zero may be harder than many of the wars he survived.

His situation changes when he meets Alna, a horned girl who understands the plains and their people far better than he does. With her help, Dias begins learning how to build instead of destroy, and how empty land can become a home if he can attract people, protect them, and earn their trust.