Sage vs Zoey, huh?
Okay, here we go.
Sage is very laid back about MC's other relationships for the most part. There are a few moments where she is a bit jealous such as when talking with Heather and Camila or when Maya tells her about kissing him. Mostly she is very accepting of his past. The idea of threesomes is a turn on for her and she actually feels a bit guilty about Maya, Josy and Jill being hurt. It is only over Zoey that Sage goes nuts. Well she obviously will go nuts about Jade too but I trust I don't need to go to detail over that one. So why Zoey?
Well the thing is that with absolutely everyone else Sage won. MC went around and then chose her. No one is a threat. She won. But she didn't win against Zoey. Zoey was not an option when he chose Sage. Zoey is an actual threat.
Another point is that in certain ways Sage is actually very inexperienced. She has obviously had plenty of sex and other boyfriends, but MC is the first truly emotional relationship she has ever had. Sage is shown to worry about this quite a lot and actually comments on how easily MC talks about emotional matters. So how did he get so good at that? Well through his first relationship obviously. In other words with Zoey. Zoey = threat.
We of course know that MC's and Zoey's relationship had quite a few issues. They never labelled it as a relationship and took a lot of things for granted which is ultimately why it didn't survive as a long distance relationship. Sage however is in the dark about this and it's very natural for her to be worried. During the phone conversation she gets a much better idea of what Zoey is to MC and they make up. He has moved on so Zoey is much less of a threat.
But MC's attitude was largely based on the idea that while Zoey was his first love the feelings weren't mutual. Zoey's confession shows him to be wrong about it and that Sage was right to mistrust her.
At the end of the episode he hasn't really had much time to collect his thoughts and it's understandable that the choice of telling Sage about Zoey's confession was pushed to the next episode. I'm not at all sure how the story will evolve from there, but expect the choice of telling Sage to come when the adrenaline of getting Derek to the hospital has worn off. They probably won't have that talk actually at the hospital, but I hope the option to tell Sage comes either that night or on the next day.
Regardless of how things work in typical real world cases, I think the game will demand telling Sage in order to get her best ending. That seems to me to be that right choice. Tell Sage the right way about it. Tell her that she was right about Zoey and that he chooses Sage. Tell her that he still wants Zoey's friendship, but gets that it might not be possible. And so on.
Hmmm... I better stop imagining that conversation or they'll end up getting married in my head. Again.
Although I do agree that isn't the same as meeting him.
