|Japanese name:||美浜 ちよ|
She is 10 years old when she first enters high school, but despite the age difference, she gets along with her older classmates. Aside from being seen as impossibly cute, Chiyo is a nice girl—a peacemaker who tries to stop any bickering and generous by nature. Her friends sometimes take advantage of her good nature and scholastic abilities. Her biggest weakness is that she is terrible at sports—she is not only five years younger than her peers, but small for her age—which leads to a lack of confidence because she feels she is a burden. Additionally, she claims she is bad at tongue twisters. Her March birthday parties are an annual celebration for the girls. Chiyo is closest to Osaka, who is most like her in naivety, and Sakaki, with whom she shares an interesting relationship: Sakaki covets Chiyo's small stature, cuteness, and warm relationship with her dog, Mr. Tadakichi, while Chiyo longs for Sakaki's height and imposing air. Osaka frequently daydreams about Chiyo's pigtails, imagining that they detach, speak, move on their own, are used to fly, control Chiyo's mind, or even cause her death if removed incorrectly.
Her parents, who are never seen (not counting the strange yellow cat-like creature dreamed by Sakaki and Osaka that claims to be her father), are very wealthy. Despite this, she has an extraordinary lack of ego, being surprised that her family's large house and summer beach home impress her friends. That she takes so casually experiences that even moderately well-off Japanese would envy frequently brings the wrath of Yukari-sensei on her head. For example, she takes no interest in expensive food such as snow crab and Matsuzaka beef.
Despite her athletic ineptitude, Chiyo is a devoted fan of the Yomiuri Giants. She loves cooking and is the wonder of her classmates for getting up early enough to make her own lunches. She is very proud of being a high school student and works tirelessly to live up to that status. In the manga, when seeing a movie with her friends, she proudly asks for the more expensive high school student admission rate. She also periodically takes a part-time job at a fast-food restaurant with Osaka, because she felt this is something a high school student would do—although some patrons were nonplussed at being served by a 10-year-old girl who could barely see over the counter. Ironically, the restaurant manager gave her the job because he thought that such a young girl must have a very poor family if she's looking for work.
Admittedly, part of Chiyo longs for the carefree fun of being a child in grade school, something of which her high school life does not often allow her. Another part of her, however, desires a physical maturity that matches her academic status—and will make others take her seriously.
Early senior year, Chiyo announces plans to attend a university in the United States where students who skip grades have done well. In consequence, she does not take the college entrance exams her friends must deal with. It also leads to some especially bizarre fantasies on Osaka's part, who imagines Chiyo as a kidnap victim, President of the United States, and the original of a series of tiny Chiyo-clones working in every airport. It is unknown whether she plans to return to Japan after her studies.