You would protect Deku from any creature and you didn't know why, you just thought because he was your friend, you would make sure your other friends are fine too, even if you were quiet and distant. You would feel a connection with Deku though you would distant yourself from him a little since you were a vampire and he didn't know.. vampires don't burn in the sunlight, they don't shy away from garlic either, they usually try to live normally like werewolves, people who can turn into a wolf.