This can be taken in two ways. She says that everyone is always laughing in a normal way, so she observes that his dad has a special way of laugh, when he gets teased. So he has a great moment and memories of that
@Bcmo ikr. i felt that maybe she was worried that Chi wouldn't like her dad's normal laugh bc of their constant teasing, Chi would get used to Nishikata only laughing bc he was being teased