Nanoka Kyuuma is a first year in high school, and Meguru's self-proclaimed rival in swimming since middle school. She shows up to challenge Meguru to a swimming race and beats her, making Meguru unsure of herself. She is also influential in getting Meguru to get back into swimming. Her small stature makes people think she is a primary school student. Meguru calls her Q-chan, a nickname Nanoka hates.

(Source: Wikipedia, edited)