Gaa-chan is a small, yellow, duck-like figure who lives within an animation studio, beginning existence as an inanimate object floating placidly in a pond outside the studio before magically coming to life. This character is the best friend and constant companion to Baja, a small badger-mouse creature who also resides in the studio, and their inseparable bond forms the emotional core of their shared narrative. Gaa-chan’s personality is conveyed through actions rather than dialogue, characterized by a gentle, curious, and playful nature that complements Baja’s sense of wonder. Together with Baja, Gaa-chan is motivated by a deep-seated curiosity about the wider world, particularly the ocean. This longing is sparked after overhearing the studio director, Kanako, express her own wish to visit the sea, prompting Gaa-chan and Baja to use magic to satisfy their curiosity and experience the ocean through a shared imaginative journey.

In the story, Gaa-chan’s primary role is as a loyal companion and a catalyst for adventure, participating in daily explorations and magical experiences within the studio. The most significant relationship is, of course, with Baja. Their friendship is frequently symbolized by a signature pose in which Gaa-chan is depicted gently holding Baja’s tail, a visual shorthand for their trust and closeness. Gaa-chan also shares magical experiences with the fairy Coco, who guides the pair on their adventures. A key moment in the character's development occurs when Gaa-chan is caught in a dangerous current during the magical ocean fantasy, an event that tests the strength of the bond with Baja and drives the narrative forward as Baja works to save the imperiled friend. Gaa-chan’s most notable ability is simply being able to come to life from an inanimate state, allowing for participation in magical events and adventures that would otherwise be impossible for a simple object.