from what I read in WN: after Ryouma helped the Rozeria kingdom win the civil war, that incompetent queen - despite not wanting him to be around her as Ryouma is a commoner - refuse to let him go on adventuring as she fears that Ryouma could be a threat if he's recruited by other kingdom. So, in her attempt to control him she gave Ryouma a title as lower noble and an unprofitable yet dangerous territory known as Wortenia peninsula, you can bet that Ryouma will aim to ursurp the throne and plan to conquer other kingdom