Looks like best girl Kana got all the treasure. Height, badonkers, shyness, and caring personality.She traded height with oppai.
Seeing her behaviour she feels like the usual transfer student that have to follow her family around the country and changes school no stop, making her unable to have friendship and grow jaded, ending up with just isolating herself to avoid another farewell.
Could even just be that she had problems in her previous school with fake friendly classmates and decided to avoit betrayal again.
Doesn't seem like a rival to me. Actually seems like one of my theories is coming true about new girl (Mafuyu). Hinaa is going to get more invested with her than Teru from this point because Teru is more situated to his new home now.please don't be a rival please don't be a rival please don't be a rival