So Koyun closed off because she couldn't forgive herself for breaking someone's heart? What else does she expect would she do? Stay in a broken relationship? I'm confused.

This series has reached a sort of odd stage. We finally got some details about Koyun's history with Igarashi, which had been treated all along as if it was horrifying and awful, and specifically that he was some sort of villain, but what we're getting finally is that that's apparently not the case at all - that like so many other things, it had much more to do with Koyun's failure to deal well with an awkward situation.

I say it's gotten sort of odd because at this point, that surprise isn't as surprising at it would've been earlier on.

It strikes me, thinking about that, that the basic arc of this series has been personal growth, but not just as seen from outside, as is common. Instead, the whole feel and tone of the series has changed as it's gone along, because the protagonists - mostly but not entirely Koyun - have themselves changed. All the way through (as neatly illustrated the first time that Minato took the protagonist role), what we've seen has been the events as seen through the eyes of the current POV character, and that's led to some notably different versions of the same events. But not only has the story changed as different people have been the focus, it's changed even as seen and recollected by the same person (again, mostly Koyun) simply because she's changed. She's seeing things differently now than she did in the beginning, and as a result, so are we.

And that's a pretty neat trick really.

I'm definitely going to have to rewatch this. I suspect it's going to be even better the second time through, because I'll know what to watch for and be better able to see how the characters and the story evolve together.