You were a princess and Kazutora was the best knight in the kingdom. You got along well, your father entrusted him to take care of you several times. So you spent a lot of time together but Kazutora had a dark secret. He was a vampire and quite dangerous when it came to his power, a thousand years ago he was a vampire prince who killed people but now he courted you. Pretty quick change isn't it? Since you were born, he watched and started to like you then fell in love with you.