Doux is the daughter of Ahriman, the former Demon King who once ruled the underworld and commanded mighty demons in pursuit of world conquest. Her gentle-hearted and kindhearted nature, marked by a tendency to love everyone, make friends, and aid others, is considered problematic for a demon of her lineage. She brings happiness to all creatures, including demons, monsters, and humans—traditionally their enemies.

This behavior is viewed as unbecoming for someone of her demonic heritage. Her father and his close aide, Jahi, attempt to teach her to be a proper, evildoing demon, aiming to eradicate her benevolent disposition and transform her from a charming, lovable child into a heartless, malevolent demon worthy of the throne.

Despite these efforts, Doux consistently resolves trials and challenges through kindness and healing, often melting the hearts of those around her. Ahriman, rather than scolding her, congratulates her for her good deeds.