Galilei Donna centers around three sisters, Hozuki, Kazuki, and Hazuki, who are descendants of the famous Galileo Galilei.
Despite their shared lineage, the sisters have drastically different personalities and struggle to get along.
Their lives are turned upside down when a mysterious organization targets them, believing they hold the key to the "Galileo Tesoro," a supposed discovery of Galileo's.
Forced to flee on an airship they built, the sisters must navigate both the dangerous pursuit and their own strained relationships.
The anime explores the mystery of the Galileo Tesoro, the motives of the organization, and how the three sisters will learn to overcome their differences and work together to survive.