It was based on a meme that went around LJ in August 2005. In response to the question "Sasuke/Faith or Sasuke/Duo?" I somewhat jokingly said they should have a threesome. Asuka said it sounded interesting, and suddenly I had Faith's POV section of chapter 1 in my head, more or less all of a piece.

So yeah, while figuring how to create and justify a Faith/Duo/Sasuke menage a trois isn't the ONLY point of "Lemonade," it was definitely the original point. It's fun to try making utter crack seem logical and inevitable. *grin*