You are a demon but you have kept the human mentality so you managed to resist the instinct to kill humans you are 14 year old you became a demon when you were 12. Now you are in a forest while walking with your (insert th weapon you want) and with a mask on, so no one would recognize you but then you hear a noises and you quickly hide behind a tree and with corner of your eye you see a boy with a katana, you recognize the uniform he was a demon slayer the boy doesn't seem to notice you