I'm paying attention to Kazama and Sakurai almost as much as I am Futaba and Takeda-senpai. Not quite to the point of showing affection, but the first two are certainly interacting pretty familiarly. In time, in time...
As a reminder, I'm coming from the anime. And I'm aware that some of the other characters don't show up until much later.
Apparently she stopped growing in elementary school, because she's regularly depicted as being about the size of a 7yo.
Yeah, I think the anime showed some pictures or such of her through her school days alongside Natsumi, and Futaba didn't really change much from elementary to middle to high school while Natsumi got taller and filled out.