Ashibe Ashiya is now a third-grade student, and his life continues to be anything but ordinary. He remains inseparable from his beloved pet, Goma-chan, a playful and energetic spotted seal pup who goes with him everywhere. The story follows the pair as they navigate the familiar yet always unpredictable challenges of elementary school life, from making new friends and dealing with homework to causing cheerful chaos in the classroom. Goma-chan, with his signature Kyu Kyu cry and boundless curiosity, often becomes the center of attention, unintentionally turning everyday situations into comic adventures.

The setting is a blend of Ashibe's home, his new third-grade classroom, and the surrounding neighborhood, which comes alive during seasonal events. Key figures from Ashibe's life return, including his best friend Sugao Anan, who often finds himself caught up in Ashibe and Goma-chan's antics. The series explores the slightly more complex social world of being a third-grader while maintaining its lighthearted, slice-of-life charm.

Notable narrative arcs in this series include the premiere episode where Ashibe must explain to his new teacher, Mr. Kanemitsu, why a seal is attending class, leading to Goma-chan becoming an accidental hit with the students. Another arc follows a chaotic trip to a summer festival where Goma-chan gets lost, is mistaken for a prize at a game stall, and causes havoc at a goldfish scooping booth before a heartwarming reunion under the fireworks. The dynamic between Ashibe and Sugao is further explored when Sugao receives a mysterious letter, and Ashibe and Goma-chan’s well-meaning interference leads to humorous misunderstandings. A rivalry develops when a new student arrives with a high-tech robotic seal, prompting a series of contests that ultimately highlight Goma-chan's natural charm and empathy. Quieter moments are also featured, such as an episode focused on a rainy day where Ashibe and Goma-chan must find creative ways to entertain themselves indoors, emphasizing the cozy, healing nature of their domestic life.