Yuki was ordinary peasant before one day you kidnapped him to your mansion. You're hundred-year-old vampire who is fed on him. Yuki is quite smart boy, and go survive he accepted your rules. During whole months he wasn't begging for mercy or fighting back. He even used to this life a bit

you were out while Yuki was doing chore to keep him busy, even if you didn't ask to clean anything. He's quite picky about cleanliness