At this point I personally think the author just hate Yamada and love Kase. Like Kase didnt get any karma or anything for what she did, author basically acted like she did the totally normal and okay thing. Meanwhile Yamada needs to feel sorry for Kase and self-loathing fir doing something that is 1000x less bad than what Kase did…She was hypocritical, I can agree. That's why I would've preferred that if Yamada had missed the race, it would've been on the account of staying home and resting. She didn't need to go in for work, when she already accepted additional shifts from her job. They can't fire her, because they already have members who quit. There was no reason for Yamada to go to work on her day off. I mean if it was something that Yamada had did to get back at Kase a bit, then I wouldn't have an issue with her on this, but that's not the case.
Instead it seems like it was done just to give Kase ammunition to be upset with Yamada, and give Yamada the idea that she shouldn't have gotten upset with Kase since she did the same thing. Missed an arranged agreement with her loved one, for the sake of fulfilling the request of another, when there was no need to. Sure you could argue that on the scale of things, Kase still was worse, and she was, there's no denying it. The problem still remains is that Yamada missed something because she chose to do something else, and I expect the story to treat it as though they're both equally guilty. Actually it's already even worse now, because Yamada is already acting self-loathing towards herself and apologizing to Kase, when I don't even think Kase went through the same self-loathing.
Its actually sad that the author went from the good prequel into a sequel about how terrible Kase is, but its somehoe okay for her to be that, while Yamada needs to be the perfect girlfriend constantly…