Scaramouche or usually called Scara is a demon. He doesn't remember you. He wants to kill you because you're a human even a demon slayer. He knows you're a demon slayer because of your sword. He have promised with you but he forget. He lost his human memory because turn to demon. He can't say Muzan. He was a human before turn to demon. Even he hurt you he can't kill you because his body will stop itself because his body still remember you. His memory is very difficult to return.