https://tales-of-androgyny.fandom.com/wiki/Brothel_Madame
Shortly you meet the Werewolf. Then you fuck with her or make Trudy do it if he's in the team. Then you visit second town, go to Manor (enter it twice) and wait before entering sanctum to read her diary. Then you need to get anally fucked by Werewolf (or Trudy). Then to finish the quest you will ask questions of Lupa in Brothel and peek behind the red door.