Renkin Kizoku no Ryouchi Keiei

A thirty-something corporate slave is reincarnated as Cain, an aristocrat in another world. Cain is still ten years old and lives a life of luxury in the royal capital, but when his father falls ill, he is sent to his territory as the lord's representative. He thought he could relax in the countryside, but he soon finds his territory in ruins and with huge debts. Riots occur one after another, intervention from the neighboring earldom occurs, and he is forced to take on mistresses called maids—will the prestigious Carlier family be able to make a comeback? Armed with alchemy and cheat knowledge, Cain's challenge begins!

(Source: Futabasha, translated)