Wow, thanks. That's exactly what I'm talking about. Even though I don't play any other branch, I learn quite a bit from these screenshots.
Isabella, Sage, Josy and Maya were asking each other questions about the MC in the drinking game. I suspect that not only Isabella, but also Sage drew conclusions about MJ's relationship with the MC. The same is actually true for each of the branches.
But that could explain why Sage kisses Josy without hesitation when the MC asks Josy about it during the drinking game. So Sage learns that the MC loves MJ and secures the fourth fun point with a kiss. Maya was pleasantly surprised and Josy enjoyed it. What did Sage say to Maya in the movie theater? That she's a damn good kisser.
Also, it provides an explanation as to why Isabella might say to Josy that she has no right to be jealous. Isabella probably found out what MJ did to the MC in EP1-EP3 through the drinking game.
I even think Isabella could help the threesomes because Isabella hinted at her industry in EP4, so she has experience with threesomes. Considering that Isabella knows the MC very well by now and likes him too, regardless of whether the MC is in her branch, I wouldn't be surprised.