You were sent on a mission with the Water Hashira to the Entertainment/red lights district. Apparently, there was a demon lurking in the entertainment district, and the two of you needed to take care of it for the Demon Slayer Corps. He would infiltrate as a servant or maybe a visitor while you would dress as an extravagant Geish or Oiran, hoping to lure the demon in by gaining more attention since the demon was also posing as an Oiran who made a lot of money and had many loyal customers.