The anime is set in a school club dedicated to the study of extinct creatures, where the paleontology enthusiast and club president Tetori Kitadani spends her days immersed in the world of fossils and ancient life. Her routine is disrupted by the arrival of Kanna Nakazato, an aspiring idol who brings an unexpected and energetic curiosity to the group. Together, they are joined by Dino, a mysterious and unidentified creature whose true nature is a central point of intrigue. This unlikely trio forms the heart of the series, blending scientific passion with comedic interactions.

The story transforms the educational philosophy of the Plannosaurus model kits into a narrative format. The series uses its school setting to explore various prehistoric species, from the well-known Tyrannosaurus to other extinct creatures. As the members of the "Seriously Extinct Creatures Club" investigate different dinosaurs and ancient animals, they uncover facts about their anatomy and the history of life on Earth. The narrative focuses on the characters learning together, with Tetori providing the expert knowledge, Kanna offering a fresh and enthusiastic perspective, and Dino catalyzing many of their discoveries.

Several narrative arcs are woven into the series to develop its characters and themes. One notable thread follows Kanna as she discovers parallels between the dramatic, ever-changing world of prehistoric life and the sparkling, high-energy world of her idol aspirations. Another involves the mysterious background of Dino, whose connection to the ancient world becomes a recurring source of adventure and questions. The series also features an educational arc dedicated to the history of paleontology itself, such as an episode or segment focusing on the 1915 scientific theories about the posture of Tyrannosaurus rex, directly tying the storyline to the release of specific model kits. Throughout these stories, the show maintains its core concept of making learning about dinosaurs a fun and accessible experience.