The Frontier Lord Begins with Zero Subjects (Manga): Tales of Blue Dias and the Onikin Alna: Volume 3 by Fuurou

With the Nezrose Domain expanding, Dias realizes that he needs to prepare for winter, which means a more stable and self-sufficient food supply. He decides to try his hand at cultivating farmland, but he’s about to find out that nothing grows on the grassy plains except for, well, grass. Unbeknownst to Dias, however, some kind of force is at work upon the soil, and the twins Senai and Ayhan hold the key to making the land fertile once more.