My Rules: Never Love, Never Lose

Isaac Litt is the son of a concubine in a house of viceroys, and his coming-of-age ceremony goes badly enough that the family treats it as a joke. Told to pick a fief and take wives, he asks for the barren mountain land nobody else wants and for three women the household has written off, all three with convictions against their name and debts to settle. He gives himself three years to clear what they owe. He was an engineering student before he woke up in this body. The fief grows almost nothing, creditors follow him out to it, and bandits from the Black Wind camp raid the area. He smelts iron, works up black powder and fires it out of bamboo tubes, and distills flower essences fine enough to sell to people with money. When the drought comes he puts together shells that can be fired into cloud to bring rain. The debts come down, the raiding stops, and his three wives take over enough of the running of the estate that it starts to pay. Rivals move against him once the fief is worth having.