Nanoka Kyuuma is a first-year high school student who serves as a self-proclaimed rival to Meguru Watase in swimming, a dynamic that began when they were in middle school. She appears at school specifically to challenge Meguru to a race and wins decisively, which shakes Meguru’s confidence. Despite this initial confrontation, Nanoka plays a key role in encouraging Meguru to return to the sport, suggesting that her motivations are not purely antagonistic but also stem from a desire to push her rival and rekindle Meguru’s own passion for swimming. Nanoka is notably small in stature, often mistaken for a primary school student, a trait that contrasts with her bold and outspoken personality. She is highly confident in her abilities and can be forward and cheeky in her interactions. Meguru refers to her by the nickname Q-chan, a label that Nanoka openly dislikes. Her role in the story revolves around her rivalry with Meguru, and through this relationship she influences Meguru’s personal growth and re-engagement with swimming. No specific supernatural or athletic abilities beyond exceptional swimming skill are highlighted; her primary attribute is her prowess in the water, which she uses to assert her status as a challenger.