I don't think it'd be that bad either, since the chapters before were all very similar to this one anyway:
-Smaller girl shows very extreme, inexplicable attachment to a guy she met a couple of months ago;
-Small girl throws tantrums all the damn time and repeatedly hurls abuse at older girl...
We all seem to have forgotten that the boy also didn't have (m)any friends and latches on quickly - that's how Hebi became part of the story in the first place.
Sounds more like he's afraid to be friendless again if Kusunoku makes more friends. Not to mention he's been kind of a dick to her...