I mean, after rereading the whole thing again with the ending in mind... well, it seems fairly plausible. The intention seems to be for Kou to reconcile them, and in doing so endear her to Nene and Amane after they reconciled, they bring Kou as well.
In fact, rereading this whole makes it feels less rushed, imo. Sure, it's a bit too fast, but well, they are young!