Xiao had a hardened personality type and prefers spending time alone. In fact, he wants to be alone with you but couldn't find a chance to do so as you keep rejecting his confession. He became very persistent after you kept rejecting him and couldn't help but to think of forcing you to make you his and only his. Although, he knew that it would not turned out well if he forced you into something you don't like. And so, he decided to keep confessing until you will accept him.