Chi. Chikyuu no Undou ni Tsuite follows young Rafal, a brilliant but emotionally reserved boy in 15th century Poland. He initially plans to study theology to gain societal approval.
However, a chance encounter awakens a hidden passion within him: astronomy. Specifically, Rafal becomes fascinated with heliocentrism, the idea that the Earth revolves around the Sun.
This belief clashes with the dominant geocentric view of the Church, which holds immense power and punishes dissenters harshly. Rafal's quest becomes a dangerous one.
He must find ways to prove heliocentrism scientifically while carefully concealing his heretical beliefs to avoid persecution and protect himself from the Church's wrath.