@RNDM1 Yeah, people were most likely not expecting to have to brain with this series. But, this also presents another psychological aspect, about how people do not change their initial opinion about someone, no matter how much they change over a given time. This is why 1st impressions are important.
I admit, I too, was not expecting such a deep psychological trauma to present itself.
Being constantly compared to others, especially siblings, can create a powerful inferiority complex.
It is even worse during adolescence, developing feelings of envy, jealousy, contempt, etc. These cause hatred, anger and disdain towards others, namely the sibling, but also eventually spreads to anyone and everyone.
Which is what we see happening to Hiiragi. She is pushing everyone away to avoid more comparisons, acting aloof and distant.
The biggest problem is that she does not know where to vent her frustrations, so she bottles them up inside.