Sadde feels... strange. They poke that feeling this way and that, trying to make sense of it, and tentatively conclude their crush on Chelsea, with whom they hang out somewhat frequently, is the cause of it. And the fact that she's bi and Bella isn't. And she's so nice and pretty and cute and she gets them, and sure, Bella gets them, too, but it's- different somehow, even if they can't quite put a finger on what the difference is. It just is.
They don't have fights. There isn't conflict, per se, in the relationship. Just a sort of... unease. A loss of synchronicity. They're sure as soon as Chelsea goes (must she? She could stay...) everything will come back to normal, even as they fall further and further in love with her.
Unrelatedly, one day Lorica's patrolling and gets a report about a building near her where no one's answering any doors.