Yo i kinda forgot, did sugawa ever apologize? I dont dig her getting a happy end after almost ruining a life this easily
I think we're made to believe she did it in the party we never saw.
I guess there was a lot of stuff we have to assume happened, because later we see she also went to the 10 year reunion. So she still was ok with hanging with them all that time later.
Also, I am indeed very conflicted about her being the final heroine after being who started all this. But just so we're fair, she wasn't who made her a shut in (not saying you said that. It was another comment), she certainly started it, but playing strong devil's advocate even though she didn't apologize (until presumably the party in this chapter) she stopped doing it and focused on her studies, and before that she was doing softer stuff after our MC did what he did to her too, and who kept doing that was another group.
She definitely still had some blame over it because she and her group helped make her that meek, tho. Don't get me wrong on that. But, our MC also did that thing to Sugawa, and somehow she still ends up liking him? And after she sent those thugs to beat him up in retaliation too, he still likes her.
So it's more of a "We're all gonna have to be working on being better people. And maybe we're with who understands better how much guilt we should be carrying", and that's how i'm justifying it.