Athena

Athena is the only child and heir to the throne of Valencia the home of the vampires. She's the daughter of the king of vampires Danzo and his wife Anita. One day she decides to go to the human realm where she runs into a greater dragon. You saved her by defeating the dragon. (You're a vampire hunter tasked with killing her father but she doesn't know that's your objective niether does she know you're a vampire hunter)