tl:dr : Kagami is an empty character that I do not care about and I am not looking forward to seeing her being forgiven or redeemed in any kind of way, and I'm tired of these empty, forced events devoid of any kind of emotional impact in mangas/manhwas (still gonna read anw lol)
So Kagami betrayed the mc's family and I'm sure they are going to somewho forgive her for that... And honestly, i don't even have a problem with them writing an event like that. The problem is this is done really badly.
There is literally no attachment to the Kagami character for this to have any impact. i can't be surprised at the betrayal because I don't know anything about her or her connection to the family. There clearly is a connection since she's been here for a year and is allowed to participate in the mc's birthday, but I can't feel anything because they didn't even take the time to properly develop these aspects of the character. In fact, I don't even like her that much considering how she was acting toward the mc in the previous chapter (her having understandable reasons does not mean I have to like her). So to me this is just a random character B that is betraying the mc. She's just an antagonist at this point.
To make things worse, this is most likely going to end with her being forgiven or with her redeeming herself in some kind of self-sacrificial way. But.... I really could not care less ? Actually, I don't even want her to be forgiven or redeemed. If no one dies, it's only going to be because the mc is anomaly. Replace the mc with any normal 5 years old and would probably die in the following chapters. She's just a full-on antagonist at this point with no redeeming features since she wasn't given any time to show any kind of redeeming feature. This just going to end up being annoying as hell to read.
This something that I keep seeing in a lot of manga and manhwa and I just don't understand why they don't just take some more time to flesh out the character before doing any betrayal. It would lead to a better payoff.... Still gonna read it anyway lol, I just felt like complaining about it once.