This is dumb.
I understand what the author wants. This sort of 'karmic retribution' thing is, to a certain mindset, the cleanest outcome because
a) the dad is viciously attacked and thus in a sense gets to feel what his daughter felt (though if I'm being honest the "is this what my daughter felt like when I beat her?" moment is also profoundly stupid because he previously made no bones about the fact that he beat his kid. He even used words like "beat" so he clearly understood the context. If they wanted that moment of relaization then he should've, til the bitter end, insisted that what he was doing was "just discipline" or "correction" or acted like he was going easy on her.)
b) He gets arrested and goes to jail as he should given that he beat his daughter regularly for years.
and
c) All of this happening away from Kotori means that she isn't involved in any of it and her name is "kept out of" what happens to her dad. Because this is Japan and it would be worse for her to be known as the victim of abuse than it would be to get the satisfaction that he has his actions exposed and faces real, direct consequence for them instead of the cosmos going "well here, I'll give you this thing that's sort of the same so that we're cool again."
It plays into the idea that 'shaming' the victim by acknowledging the abuse perpetrated against them is a bad thing and is worse than just getting over it and moving on. The same thinking that leads to the fact that the low publicly cited crime statistics regarding abuse, both violent/physical and sexual, are actually gross underrepresentations of reality because the crimes aren't taken seriously and victims are either encouraged to stay quit to avoid rocking the boat and save face, or are outright told that they must've done something to cause the abuse and should instead use it as an 'opportunity' to fix themselves instead of actually addressing the person responsible.
So all of this happens because the author can say this is the best outcome by virtue of punishing the dad indirectly while getting retribution for Kotori that doesn't require her to be involved and pick up the stigma (or, worse yet, be ignored or brushed off thus compounding her mental issues). Everyone wins if you subscribe to the narrow, conservative, old-school Japanese definition of winning!
And it's garbage. The far more satisfying conclusion would've been if the cops showed up and arrested him while he was standing threateningly over his clearly beaten daughter so that he faced the actual justice for his crime rather than a sort of indirect universal make-good. The author already fully showed the dad being an abusive scumbag and this chapter gives him rationale that makes sense but also in no way excuses what he did. That's a positive step. So take the next positive step and have a more plausible, direct outcome that addresses the issue rather than this contrived nonsense.