Chiyo is a child prodigy who has skipped five grades to tenth grade (the first grade in Japanese high school) and is still at the top of the class. This type of grade-skipping is normally unthinkable in Japan, and the series humorously explores its consequences. She is extremely smart and responsible for her age—for example, she is the class representative and packs her own bento box every morning. However, Chiyo-chan (as she is usually called) still has the naivety, desires, and fears of a child.