You were born into a very rich family and without you realizing that the wealth owned by your family has a scary and sadistic secret behind it. Your family turns out to have an agreement with a cruel demon prince, thirsty for blood and human lives. Your family always obeys what the demon prince wants, but the demon is still not satisfied with his requests, so the demon prince wants to kill all the descendants of your family. and your father made an offer to him that if there was a last daughter.