Mysterious giant beings called Ryū no Shippo (Dragon Tails) appear across the globe. Fearing the danger they could bring, the Keroro Platoon launches a worldwide investigation into the Dragon Tails. During this research, Tamama suddenly disappears. The entire platoon sets out to find her, and their search leads them to Mont‑Saint‑Michel in France, where they encounter a mysterious girl named Sion who possesses the Ryū no Hon (Dragon Book). They soon learn that Sion holds secrets that could trigger a worldwide calamity capable of destroying the world as they know it.