Yūma is a human child living in Kasukabe who becomes one of the children captured by the Rakuga Kingdom's military forces. This capture is part of the kingdom's strategy to force children into scribbling activities, desperately needed to generate energy. The floating kingdom faces imminent collapse because the creative energy derived from children's doodles in the human world is fading. While held captive to produce these vital scribbles, Yūma's mother actively searches for them, highlighting the familial concern caused by their disappearance. Yūma is among the group targeted by the kingdom's enforcement operations, whom Shin-chan and the "Almost Four Heroes" race to protect and rescue. Their successful rescue hinges on the power of the "Miracle Crayon," the key artifact used to restore balance between the kingdoms. Within the film's conflict and resolution, Yūma's role underscores the impact of the kingdom's actions on Kasukabe's children and their families.