"Eiga Crayon Shin-chan: Ora-tachi no Kyōryū Nikki" is a feature-length anime film that blends comedy, adventure, and family themes, centered around the mischievous yet endearing Shinnosuke "Shin-chan" Nohara. The story begins when Shin-chan and his family discover a mysterious egg during a camping trip. The egg hatches into a baby dinosaur, which they name Kyōryū-chan. The Nohara family decides to care for the dinosaur, forming a close bond with it. However, their lives take an unexpected turn when a group of scientists, led by the ambitious Dr. Futaba, learns of Kyōryū-chan's existence and seeks to capture it for research purposes.

As the Nohara family attempts to protect Kyōryū-chan, they are transported back in time to the Cretaceous period through a time portal created by Dr. Futaba's experiments. Stranded in a prehistoric world filled with dinosaurs, the family must navigate the dangers of this unfamiliar environment while searching for a way to return home. Along the way, they encounter various dinosaur species, some friendly and others hostile, and learn valuable lessons about survival, teamwork, and the importance of family.

The film explores the dynamics of the Nohara family, with Shin-chan's playful antics providing comic relief amidst the perilous situations they face. Misae and Hiroshi, Shin-chan's parents, demonstrate resilience and resourcefulness, while his younger sister, Himawari, adds an element of innocence to the group. The bond between the family and Kyōryū-chan deepens as they work together to overcome challenges, highlighting themes of love, responsibility, and the interconnectedness of all living beings.

The narrative builds toward a climactic confrontation with Dr. Futaba, who pursues the family into the past with the intent of capturing Kyōryū-chan. The resolution emphasizes the importance of coexistence and respect for nature, as the Nohara family ultimately finds a way to return to their own time while ensuring Kyōryū-chan's safety. The film concludes on a heartwarming note, reinforcing the enduring strength of familial bonds and the impact of their extraordinary adventure.