Comical adventure story starring Kasukabe Defense Forces and dealing with "food" as theme. Kasukabe Defense Forces (Shinnosuke and his mates: Kazama-kun, Nene-chan, Masao-kun and Bo-chan) decide to attend "B-class Gourmet Carnival", a big event in Kasukabe, without their parents, to eat very tasty yakisoba sauce cooked by "Sauce's Ken". On the way, a mystery woman asks them to bring a legendary sauce to Sauce's Ken. They head to the event site with the sauce, but they wander off into a mountain, and "A-class Gourmet Organization", an organization plotting to eliminate B-class gourmet, seeks to take the sauce away from them.

Watch Crayon Shin-chan Movie 21: Bakauma! B-Kyuu Gourmet Survival Battle!! Online