Modern Zouping girl Xiao Yi passionately loves mathematics but is careless and impetuous. Due to a bronze puzzle mold, she accidentally time-travels to the Wei and Jin dynasties, encounters her idol—the mathematician Liu Hui—and becomes his disciple. Because the mold is lost, Xiao Yi temporarily stays at the study, studying mathematics and solving folk mathematical problems with Liu Hui, while also facing Lord Xun's repeated harassments. Under Liu Hui's personal teaching of 'seeking truth from facts and using mathematics to help the people,' Xiao Yi gradually gets rid of her carelessness and comprehends the patriotic significance of mathematics; and Xiao Yi's modern mathematical thinking also provides new ideas for Liu Hui to study the circle-division technique and measure the height of Mount Tai.