Nanoka Kyuuma

A first year in highschool, 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, and is also influenctial 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