I'm a Noble on the Brink of Ruin, So I Might as Well Try Mastering Magic: Volume 3 by Nazuna Miki

Despite the obstacles along the way, Liam’s rising nation of monsters is showing great progress, in no small part thanks to all his novel and ingenious magical ideas. However, although Liam is content just watching over the city of magic that he and his familiars are building, the surrounding nations aren't willing to leave it alone. From an eccentric princess to battle-hungry hunters, all sorts of groups start showing interest in this newly emerging power—and when the less friendly ones start jumping into the fray, Liam realizes that ruling a country will never be easy. Can he step up as the king of this magical nation and defend the land that his familiars now call home?