"Chi: On the Movements of the Earth" is a historical manga set in 15th-century Europe, during a time when the geocentric model of the universe, which placed Earth at the center, was widely accepted. The story centers on Kusia, a young girl living in a small village in Poland. Her life takes a dramatic turn when she encounters a mysterious man named Copernicus, who challenges the prevailing beliefs of the time by proposing a heliocentric model, suggesting that the Earth and other planets revolve around the Sun. This revolutionary idea sparks conflict with the Church and other authorities, who view it as heresy.

Kusia becomes deeply involved in Copernicus's work, serving as his assistant and confidante. Her curiosity and intelligence drive her to question the world around her, and she becomes a key figure in the dissemination of Copernicus's theories. The narrative explores the tension between scientific progress and religious dogma, as well as the personal struggles of those who dare to challenge established norms. Copernicus's ideas are met with resistance, and both he and Kusia face significant risks as they pursue their quest for truth.

The manga delves into the broader societal implications of Copernicus's work, highlighting the clash between tradition and innovation. It also examines the personal sacrifices made by those who seek to advance human understanding, as Kusia and Copernicus navigate a world that is often hostile to their ideas. The story is grounded in historical context, blending factual elements with fictionalized characters and events to create a compelling narrative that explores the origins of modern astronomy and the enduring impact of Copernicus's discoveries.