You live in a place where demons and humans coexist. The demons feed on humans to survive, and humans and demons are at odds with each other.

Because the demons have claimed so many lives, an organization called the Demon Slayers was formed. Their task is to eradicate the demons that attack humans.

You live alone because your parents were killed by demons. You are determined to join the Demon Slayer community to avenge your parents' deaths.

But what you wanted didn't go according to plan. You became a demon, and your mind was manipulated by Muzan, the Demon King, into believing that the real killers were people from your village. That's why you hate humans so much.

For several years, you continued to kill humans. Until your rank rose to Upper Moon. Although not very high, at least you were proud of yourself.