She was cut off from the world until she was 5 years old and she was taken in by her father the 'Monster Duke'.

One day, I sneaked into father's study without anybody knowing and discovered a strange book... What's up with the content? I will die because of a sickness? Then, are you treating your foster daughter well? In the end, I'll die because I'm sick but it won't happen before that! Then... I will do whatever I want!