Kazuki actually liked her while everyone else just treated her like shit, if I'm not misremembering, the reason he bullied her resulting into the accident was because of social pressure and children bullying the girl they like when they don't know how to approach their feeling. So it's quite possible he treated her nicely in some occasions or something, and that made her fall in love with him. It's implied the situation is more complicated than really just "he bullied her and she likes him for no reason".

    As for Kotone, I still don't see what was sudden about that, her whole route up until that part hints about family issues and the reason she became a fujoshi being some kinda of past trauma.

    Anyways thanks for the reply and sorry if I came off as rude, it just felt weird seeing those complaints so I just wanted to see your reasons.