Kyoko is the head and only member of the Eiken club's science division. Despite resembling a small child she is older than she seems. Even though from a photograph taken from when she was younger she doesn't appear to have grown in height much.
Although she acts tough she like's cute things, such as a fictional action hero in the series called Nekomanman.
Also she is secretly quite jealous of the other girls in the club for having such bodies while she still resembles a small child, but hides it by saying since she plans to be a scientist she doesn't need to be tall or curvaceous. In the previously mentioned photograph her mother is about as tall as an ordinary person so it might be possible that her father is quite short, or she has yet to go through a growth spurt. In a dream Densuke had Kyoko was seen to be tall and beautiful 10 years into the future.
It is also possible she likes Densuke but repeatedly threatens him when he, like with all the other girls, end's up doing something she considers perverted. Although due to her appearance it is much more downplayed than with the other girls.