What Is a Demon?

What is right? Is it because the person wearing the clothes looks decent, sanctimonious, and shouts about killing some demons? What is evil? Are they those "monsters" who are born with simple thoughts to survive and protect themselves? How do you define good and evil? If people in the world are basically good, why does the word "demon" come about? Once human nature has evil thoughts, it will enter the endless abyss... This novel and its characters are purely fictitious. Any similarity is purely coincidental and should not be imitated.