Gyakusatsu Mahou Shoujo Belial☆Strawberry

In the past, the three realms of the Underworld, the Earth, and the Heavens were separate. Demons lived in the Underworld, humans lived on Earth, and the fairies lived in the Heavens. However, ten years ago, the demons invaded the Earth. Now they rule the Earth, and all of humanity are their slaves. They still have jobs, attend school, and so forth, but they all live in fear. If a human offends a demon, even by accident or by doing nothing at all, they can't stop the demon from killing them. One...