Chiyo Mihama is a child prodigy, entering senior high school at age 10 and operating at the top of her class.
Although nervous at first, Chiyo manages to become friends with her older classmates, often playing the role of a sort of peace maker between them. She is particularly close to Osaka, with whom she shares a certain naivety. She eventually becomes closer to Sakaki as well, who comes over to visit with Chiyo's dog, Tadakichi-san (and who eventually houses her own cat at Chiyo's house).
At the end of the Azumanga Daioh manga, Chiyo-chan decides to go to university in America, where kids who have skipped grades are more common.