Hozuki, Kazuki, and Hazuki are three sisters who are descendants of Galileo. They have completely different personalities and tastes, and they never see eye to eye. One day, the girls are suddenly attacked by a mysterious organization. This organization is after the "Galileo Tesoro," which Galileo Galilei was said to have discovered. Still unaware of what is going on, the sisters escape on the airship they built following the sudden attack. However, it will not be easy for these three sisters to help each other out in a pinch when they are constantly at odds with one another. What is the Tesoro, and what does the organization want? And what about the relationship between the sisters? It is a mix of cute girls, action, and mystery!