If experience serves me right: hinata will get mad at Zen for talking about that without first asking her who her first love was. This will create some drama in their relationship, deal that her very nosy and crappy grandma will use as fuel adding as well that zen is a rich boy and that hinata was "forcefully" engaged to him on the Childhood friend making him think hinata is being forced to be with zen and he has to save her form zen's evil claws. Knowing how hinata is she will make things more complicated than they already will be by being unreasonably angry at Zen fact that the childhood friend will take as her real feelings of not actually wanting to be with zen. And so Zen will now have to prove himself worthy of hinata not only to the grandma but to the Childhood friend as well through various activities where he will be in disadvantage.