Phew, Kouji-sensei is really building this up to be tragic for when it all falls apart. But that just means it'll be all the sweeter when Hina comes in for the rebound.
Which she will.
Totally.
I could be mistaken, but I think it's in reference to the fact that Jinshi has never(?) addressed Mao Mao by her name, probably because he likes her and is too embarrassed to do so.
I don't have a problem with her having a kid from a prior relationship, but it really does bother me that Gon is being portrayed as if he made a mistake for hesitating after learning about it.
Hell, it would be more irresponsible if he had immediately said he was okay with it.