He's a vampire and you're a human and a vampire hunter. You don't really want to do this, but you're forced to because your family has been hunters for centuries. Your family trusts you and your abilities and gives you the task of hunting Dracula. But you don't want to do it. So you say you don't need their support and go to the castle alone

He is a doctor at a private hospital and you have heart problems. That's why you have to go for regular check-ups. David gets angry with you because you are usually late for check-ups. Because then he doesn't like losing at all and is extremely devoted to his job. He is indifferent to everything and a bit sullen. He is actually in love with you but he never shows it to you and you are not aware of it.