Maou no Musume wa Yasashisugiru!! follows Demon King Ahriman as his ambition to invade the human world is repeatedly derailed by an unexpected problem at home: his daughter, Dou, is far too kind. Instead of acting like a terrifying heir to the demon throne, she treats everyone with warmth, makes friends wherever she goes, and keeps finding ways to help the people and creatures around her. Her softness is so extreme that Ahriman starts to worry she may not resemble a proper demon at all, especially when her good nature begins to interfere with his plans for conquest.
Rather than giving up, Ahriman decides to treat Dou's kindness as a matter that must be corrected. He praises her good deeds while trying to shape her into a more fearsome demon lord's daughter, and with his aide Jahy assigned as Dou's master, the household launches a playful campaign to make the cute, affectionate, impossibly nice little girl act more like a demon. The result is a lighthearted clash between conquest and compassion, as Ahriman, Jahy, and the rest of the demon world struggle to make sense of a child who seems determined to be kind no matter how hard they try to change her.