Ayuko Uehara is one of the three central characters in the story, serving as the middle ground between her two best friends. She is a high school girl who is often described as the level-headed and practical member of the group, always trying to maintain harmony. In personality, Ayuko acts as a mediator and is frequently the straight man to the antics of her more energetic friends. She is somewhat shy and reserved, yet she willingly follows along with the group's activities, providing a crucial sense of balance.

Physically, Ayuko is notably short, a trait that is a constant source of teasing from her friend Kanaka Amaya. Her nickname, which evolves from Ayukong to Yukon, is directly related to her height and the playful jabs she receives about it. Despite her small stature, she is considered quite popular at school and is noted for her good grades, which fall into the upper-middle range. Her family appears to be relatively well-off, and she lives in a home with a traditional Japanese aesthetic.

Her role in the story is defined by her relationships with Kanaka Amaya and Saki Iwasawa. While Kanaka is the boisterous mood-maker and Saki is the unmotivated but talented tall girl, Ayuko is the anchor that holds the trio together. She is the frequent butt of jokes, particularly from Kanaka, but this dynamic underscores her patience and her integral place in the group's friendship. Ayuko also has a key relationship with her older sister, Hiroko Uehara, who works as a manga artist and has a very strong attachment to her, often described as a deep sister complex. Unlike the more overtly sporty Saki or the hyperactive Kanaka, Ayuko does not possess any singular standout athletic or comedic ability, but her notable skill lies in her emotional intelligence and her capacity to be the steady, reliable presence that allows her friends' personalities to shine.