Ashibe Ashiya is a lively and loud-voiced third-grade boy who lives with his parents and his beloved pet, a baby spotted seal named Goma-chan. The two have been inseparable since first grade, when Ashibe found the seal pup after it fell from a passing truck. Now a year older, Ashibe is eager to prove he has grown up, but his daily life remains a cheerful whirlwind of school, play, and small adventures with his friends and family.

The story takes place in a typical Japanese town, centered on Ashibe's home, his school, and the local streets where he and his classmates spend their afternoons. His closest friend is Sugao Anan, a boy who used to live overseas due to his father's job but has since returned to the neighborhood. Sugao is deeply fond of Ashibe and often joins him and Goma-chan in their antics. Other classmates include the gentle Yuma and the earnest Mao, who together form the core of Ashibe's social circle. At home, Ashibe's mother and father provide warm, occasionally bewildered support as the household navigates life with a mischievous seal.

The humour and heart of the series come from everyday situations: Ashibe trying to impress his friends with a grown-up attitude but losing focus when a snack appears, Goma-chan becoming obsessed with playing alone with a piece of string, or a family meeting called to debate the true nature of the pet that has lived with them for years. School events such as health checkups, new semesters, and classroom lessons offer further opportunities for gentle comedy and small moments of friendship. Through each brief, self-contained episode, the series highlights the simple joys of childhood and the bond between a boy and his unusual best friend.