Pearl's entire kingdom falls apart the moment he leaves to grow up, and his lack of confidence becomes the actual problem to solve, not just his character flaw. Shimajirou and the crew don't fix him with speeches. They drag him across an island where every locked door, every key, every challenge is his to overcome or not. A kid unsure if he deserves to be king learns that kingship isn't about being perfect, it's about showing up when your people need you, even when you're terrified.

Pearl, prince of the Glitter Kingdom, is getting ready to take the throne. After he departs for Challenge Island, something happens back home that robs the kingdom of its treasured glitter. Shimajirou and his friends team up with Pearl, a prince short on self-confidence, on a quest for three keys that can rescue his realm. The movie is a fantasy adventure with a comedic streak, built around a young royal and the friends who travel with him.