Deep in the forest lives Allen, a misanthropic wizard. He is called "Demon Lord" and feared by those around him.

One day, while living out his life as a hermit, he finds a young girl named Charlotte who collapsed in the forest. Although innocent, she was accused of committing evil deeds, had her engagement annulled, and was forced to flee her country.

Upon hearing that, Allen recalled the bitter experience of being betrayed by a party he once believed to be his companions. Hearing the story of the 17-year-old's exploitation, Allen decides, "I'll let her live in my mansion, and I'll teach her all sorts of bad things..."

(Source: Shufu to Seikatsu-sha, translated)