Elfin Rose: Toraware no San Koujo

The main character used to be a general in Saarland empire. But he raped an emperor's mistress and he was shunted off to a kingdom in the backwoods. He is the titular king now and lives a boring life. One day, a mysterious carriage falls over the cliff and there were several soldiers around the carriage. After his troops defeated them he looked into the carriage and finds beautiful sisters. He takes them to his castle and his life with the sisters begins...

(Source: Himeya Shop)