I think it comes up again when he gets double-crossed post-war and saddled with a fief in the worst section of land on the continent, the titular Wortenia Penninsula. If I remember right, he goes and gets the Inevitable Trustworthy Isekai World Slave Trader to sell him as many kids as possible, then puts them through boot-camp and turns them all into magic soldiers and has them start killing the monsters that infest the peninsular. Or something like that.