The main female protagonist and the 43rd supreme ruler of the Demon Realm who holds the title of Demon King. Even though she looks young, she is in fact over a hundred years old. the Demon King wants the best outcome for both sides of the war, and after revealing her plans to the Hero and convincing him to join forces, she sets for the Human Realm. She disguises herself as a human noblewoman known as the Crimson Scholar , and shares her vast knowledge on such topics as economics and farming. She comes from a clan of demons that prioritize knowledge. They reside in a hidden dimension called the Outer Library, which contains a vast archive of knowledge from various times and alternate universes. That place is where the Demon King gains her range of knowledge.
The Crimson Scholar rapidly grows in popularity from both her radical ideas and beauty. She is viewed with distrust by the church and the central kingdoms, who brand her as a heretic out of fear that it would loosen its grasp over the countries helped by her. To ensure a temporary ceasefire between the Humans and Demons, the Demon King disseminates rumors that her battle with the Hero indeed occurred as expected, resulting in his disappearance and her body becoming severely wounded. This provides her with extra time to complete her plans by leading her servants to believe that she cannot command them until her recuperation is completed.
Though an imposing and intelligent woman, she has shown a bit of a childish and comedic side. To appear more threatening, she wears a headband with a large set of horns. The Demon King has always held affections for the Hero and anticipated their meeting from the moment of his birth. One part of becoming the Demon King involves a transfer of emotion and power from the past Demon Kings in the Ancient Royal Tomb. However, the spirits of the past Kings possess her body when she attempts the ritual for a second time, and she is rescued by Hero forcing the spirits out of her body by affirming their vow together.