Everyone's song transforms into the courage to take a step forward! The long-awaited "Captain Hat" show is finally about to begin at Challenge Island! Mylie and Shimajiro, who lack confidence in playing the lead role of Captain Hat, get sucked into the magical "Magical Bag" and embark on an adventure inside the bag's world... Will Mylie be able to gain confidence through her adventure with Shimajiro...? In this film, just like in all Shimajiro movies, children become the heroes of the adventure! By cheering with loud voices and applause, participating in quizzes, and singing the "Song of Courage" along with the movie, they can experience the courage to take a step forward and the importance of trusting their friends. Now, let's set off into the world of adventure with Shimajiro and friends!