Galileo's descendants, Hozuki, Kazuki, and Hazuki, each possess unique personalities and preferences that keep them at odds with one another. Unexpectedly, the girls are targeted by an enigmatic organization hunting the "Galileo Tesoro," an artifact supposedly discovered by their ancestor. Oblivious to the reason for the attack, the siblings flee aboard their custom-made airship. However, cooperation between the sisters is scarce, which complicates their efforts to navigate through danger. What is the Galileo Tesoro? Why is the organization pursuing it? And what impact will these events have on the sisterly dynamic? This tale involves cute heroines, thrilling action, and a thrilling mystery!