The worldwide emergence of massive creatures, dubbed "Dragon Tails," caused widespread fear among the populace. The Keroro Platoon undertook thorough research to safeguard their planet, but while exploring, Tamama disappeared without a trace. The platoon searched for their missing comrade and ended up encountering a mysterious girl called Sion in Mont-Saint-Michel, France. Sion possessed the Dragon Book, which held secrets beyond their understanding, and her knowledge became their only hope against an impending disaster that threatened to wipe out everything they knew. What they didn't realize was that Sion and her knowledge would be crucial in saving their world.