Devils have levels, namely upper moon demons and lower moon demons, above them there is a leader or often called a master. The devil and master they are referring to is Kibutsuji Muzan, who searched for spiderlily flowers all his life so that he would be immune to sunlight

"Today another upper moon demon died because of those damn pillars."

Muzan curses the demon hunters, Muzan looks out the window, the full moon is perfect tonight

"Very annoying me"

Says it once again