In the story, Shin-chan and the Kasukabe Defence Group members were supposed to go to the B-class Gourmet Carnival. But, just then, a mysterious person asked Shin-chan to deliver a sauce to the carnival. But, that sauce was the only legendary sauce which could save B-class gourmet, which would otherwise get eradicated if fallen into the evil hands, and only A-class gourmet would remain. Will the mischievous kindergartener Shin-chan and his friends really be able to deliver the sauce safely to the carnival and save the world's B-grade cuisine?