Before she was born, Fiona's parents had been impoverished nobles (her father was a baron) who sold her to the demon Darius in exchange for regaining their wealth and power. Darius initially was going to refuse the offer, seeing no point in having a human infant but changed his mind when it occured to him that it might be an interesting change of pace from his usually dull daily existence so he accepted the offer and stayed behind as a butler to raise his new charge while Fiona's parents enjoyed their wealth, paying no attention to their daughter. They were always taking cruises and whatnot and it was just Fiona, Darius and the servants in their mansion.



Fiona adored Darius and Darius grew quite fond of her, though he disdained humanity in general. One day Darius found 8-year-old Fiona in her parents room, looking through her father's diary where she discovered that they had sold her to Darius. She confronted Darius, heart-broken about it and accused him of only pretending to care about her when in fact he wanted her soul. Darius tried to explain that he was not that type of demon but she refused to believe him and became very cold towards him, much his dismay. A few days later, a message was delivered informing Fiona that her parents' ship had capsized off the coast of France and there were no survivors, which Fiona becoming the Baroness of Ashford.



For the next few years, Fiona still treated Darius in a rather cold manner though she did eventually start warming up to him when she was around 13 years old, when he was finally able to explain fully that he intended Fiona no harm but intended on making her his wife once she was an adult.



Darius is well-acquainted with Sebastian but is not antagonistic towards him, unlike Claude though they can't be considered friends. Fiona wishes to go into the toy business like Ciel and is considering approaching him with ideas of her own for toys that Ciel might be interesting in manufactuering.