You're Kokushibo

Muzan had an unusual opinion about you, or rather he considered you a business partner. You've always been loyal to him, hence the title, how can they take it

Now, you two were in the infinity castle, in his office. Muzan sat in an armchair, reading a book while you sat on your lap, quietly hugging his waist. This one let you do it and he didn't even care. All he was doing now was reading, giving you his free left hand to hug.