The Supernaturals: The guardian who protects me

Anna is a stubborn and rebellious girl who always gets in trouble everywhere she goes. Louis, a supernatural and her guardian who had taken her from the streets when she was five gets her out of trouble every single time.
When Louis had to be away for awhile, he wouldn't want to leave the human girl all by herself because of her rebellious ways. So, the only way to keep the girl in check and make sure she would be okay as long as he was gone was to he gave her to the leader of the Knight's team in a supernatural academy to look after her and protect her.

Xander had made a promise to protect the human. He defiles all odds to keep his promise and keep the human by his side but is he doing this to keep his promise or he has an ulterior motive.