When enigmatic colossal creatures known as 'Dragon Tails' surfaced globally, the Keroro Platoon embarked on a global investigation to understand and neutralize the threat. However, their mission took a dire turn when Tamama vanished without a trace amidst the inquiry. As the team rallied to locate their missing comrade, their quest led them to Mont-Saint-Michel, France, where they crossed paths with the enigmatic Sion. Sion, the guardian of the cryptic 'Dragon Book,' harbored secrets tied to a looming worldwide catastrophe that could shatter the very fabric of reality they knew.