"Yes! Precure 5: Kagami no Kuni no Miracle Daibōken!" is a movie adaptation of the "Yes! Precure 5" anime series, serving as a standalone adventure that expands on the magical girl narrative. The story begins with the five main protagonists—Nozomi Yumehara, Rin Natsuki, Urara Kasugano, Komachi Akimoto, and Karen Minazuki—receiving invitations to a mysterious theme park called the Mirror Kingdom. Accompanied by their fairy companions, Coco and Nuts, the girls embark on a journey to this fantastical world, unaware of the dangers that await them.

Upon arrival, the Mirror Kingdom appears to be a vibrant and enchanting place, but it is soon revealed to be under the control of the villainous Eternal, who seeks to drain the happiness and dreams of its inhabitants. The Eternal’s minions, led by the sinister Bunbee, trap the Precure team and separate them from their fairy allies. The girls must navigate the deceptive and ever-changing landscape of the Mirror Kingdom, facing illusions and challenges that test their resolve and unity.

As the story progresses, the Precure team encounters a young girl named Syrup, who is revealed to be the true ruler of the Mirror Kingdom. Syrup has been imprisoned by Eternal, and her absence has caused the kingdom to fall into despair. The Precure must confront their own fears and insecurities, symbolized by the illusions created by the Mirror Kingdom, to regain their strength and rescue Syrup. Through their determination and teamwork, they manage to overcome the illusions and defeat Bunbee, restoring peace to the Mirror Kingdom.

The climax of the story involves a final battle against Eternal, who attempts to use the power of the Mirror Kingdom to plunge the world into eternal darkness. The Precure, empowered by their renewed bonds and the support of Syrup, unleash their full potential to defeat Eternal and restore the kingdom to its former glory. The movie concludes with the Precure team returning to their world, having grown stronger and more united through their adventure in the Mirror Kingdom.

The main characters—Nozomi, Rin, Urara, Komachi, and Karen—each bring unique personalities and strengths to the team, contributing to their dynamic as a group. Their fairy companions, Coco and Nuts, provide guidance and comic relief, while Syrup serves as a key figure in the narrative, representing hope and the resilience of the human spirit. The story emphasizes themes of friendship, courage, and the power of dreams, staying true to the core values of the "Precure" franchise.