Allen, a misanthropic wizard, lives deep within the forest. He is known as the "Demon Lord" and feared by those around him.
One day, while living his life as a hermit, he comes across a young girl named Charlotte who has collapsed in the forest. Despite being innocent, she was accused of evil deeds, had her engagement annulled, and was forced to flee her country.
When he heard that, Allen remembered the agony of being betrayed by a group he once thought was his companions. After 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: MAL News)