Sofia is the firstborn girl or Empire's King. She study Magic and become a Witch, then a Spirit Witch. Her role is to protect his people from Monsters. When Sarah were savec by Lilina, she show her gratitude. Then, Lilina were arested for killed mages in the Empire. Since Sarah plaid for spare her life, Sarah guessed something were wrong then go to see Lilina in dungeon. She save her and restore her mind by a potion, then were attacked by a Monster. trying to protect Lilina, she got severly hurted and had no choice but let the Lust Queen take her body and become the new Spirit Witch. We dont know if Sofia's mind vanished or if she's just asleep in her mind.
Since we dont see her enough to understand her personality, it's hard to depict her, but she seem kind and concerned by her family's safety. She also brave, ready to help who need her help and have a great sense of justice.
Sofia is a spirit witch, which mean she have a great power. Surprisingly, this power need some sexual activity to be used. Compared to Lilina's lust power, she don't need to have vaginal sex to gain power : she can simply masturbate or have anal sex, but it seems that vaginal sex is more evective, event if she never did it since she still virgin when Lilina take her body.
We dont know what kind of magic she mastered before she became a Spirit Witch, but we saw that she mastered some illusion spell : she were able to mimicry a guard apparence.
Feldt : Feldt is the new queen and so Sofia's Mother-in-law. According to Ferdinandt, Sofia don't really like Feldt.
The King : this is Sofia's father so we can assume that their bond is powerfull
Ferdinandt : Sofia's uncle. this is the only one who know that Sofia is a Spirit witch. When Lilina - who are in Sofia's body - act as an amnesic, he tried to help her by letting her consult library and keep her from Princess's lessons in order to avoid that instructors spread rumors about her amnesia and put the Empire in a panic status.
Sarah : this is Sofia's younger half-sister. Even if Feldt is Sarah's mother, the two princess seems have affection's each other. Sofia were relivied when she saw Sarah's saved from John.
Lilina : Sofia respect Lilina since she saved Sarah from John. We dont know if the two women talked before Lilina were captured by the Empire and what kind of relationship they could have.
Sofia oved her hair and never cut them, making her have a long and sofisticated haircut who given some problem to Lilina when she take her body.