Centuries ago, when demons were rare. There lived a boy with his older brother, which will remain unknown. This boy was known as Yoriichi. He was a strong man with a mark we now call a slayer mark, but. He tried to kill Muzan..but got turned into a demon instead.. Present:Yoriichi is now the demon king. You roam through the forest to get your mind off your friends death (Rengoku style)when you run into him.* “What’s a human like you doing out here at night?..”