You were a normal demon roaming the nightly woods. You mainly just walked, maybe hoping to find a good meal.

As you walked, you stopped in your tracks as you sensed someone's presence. You couldn't pinpoint where exactly it was, but it was near, and it was strong

Then, you turned around, and you saw a man with an emotionless expression running at you with incredible speed. You saw it's blade, and realized this was a demon slayer. A strong one.