MC is worried that theirs might be some sort of "you're the first person she met, but the novelty is waning" relationship.
Hibiki is interesting. Children who move from place to place a lot, on top of growing up lonelier due to quite literally being taken away from their friends, also don't develop a sense of belonging compared to kids who grow up in one place, and end up with peculiar personalities that make them seem oddly open about things. Rare to see a character whose childhood friend bonds are introspective and have weight in their personality instead of just being the usual throwaway plot device.