The Demon Queen who had personally wiped out half of humanity after experiencing the loss of her beloved dragon at a young age. The slaying of her dragon drastically changed her view and opinion of humans.
Although a monster, Sheila resembles a human girl in all aspects except for her ears, which have a triangular shape and folds that make them look like gills.
In the beginning of the first volume, Sheila at first intended to get close to Exa so she could murder him, but instead finds herself accidentally developing a romantic interest for Exa. She does not wish to kill him, but cannot ignore the fact that Exa is a threat. Sheila puts on the facade of being a meek demon to persuade Exa to take her along on his journey, so she can follow him. Ironically, Exa's journey is to find the Demon Lord and kill her. However, Exa does not realize that she is in fact the Demon Lord, who Exa is determined to kill.
Upon meeting Exa, she temporarily deserted her post as Demon Queen to join his group, and so she created a Copy of herself that would fill in her place; although mere moments after being born, Copy openly declared that she would destroy Sheila and become the "original" Demon Lord.
Sheila does not address Exa by his name, but instead calls him Hero or 'Yusha' due to her growing love for him.