Movie
Description
Kais grandfather is a central figure in the protagonist's new life in the seaside town of Hinashi. He is a master umbrella maker, a traditional craft that stands as one of the primary occupations of the town alongside fishing. His home doubles as his workshop, and it is there that he takes in his grandson after the boy moves from Tokyo following his parents' divorce.

As a long-time resident of Hinashi, the grandfather deeply believes in and reinforces the town's legendary fear of merpeople, known as ningyo. He adheres to the local lore that these creatures are dangerous, believing that they raid fishing nets and have caused the deaths of humans who fell overboard. This fear is rooted in a personal family tragedy, as it is strongly implied that his own mother was killed by a mermaid, an event that has made music a forbidden subject in the Ashimoto household. He is portrayed as a strict guardian who warns Kai to stay away from the sea and forbids him from playing music, which he believes will attract the merfolk.

Despite his stern demeanor rooted in tradition and caution, the grandfather's primary motivation is the protection and well-being of his grandson. He provides a stable, if simple, home for Kai, embodying the town's insular and cautious worldview. His role in the story is to represent the older generation's deep-seated prejudice and fear of the unknown, specifically the merfolk. This generational conflict is a key obstacle that Kai and the young mermaid Lu must navigate.

Throughout the film, the grandfather's relationship with Kai is tested as the boy becomes increasingly involved with Lu and music. As Kai emerges from his shell and forms a bond with the mermaid, it challenges the grandfather's long-held beliefs. His development is subtle but significant, as his rigid stance is eventually softened by the events that unfold, particularly when the town comes together to help the sea creatures. In a critical moment, the townspeople, likely including the grandfather as a master craftsman, use their umbrellas to shelter Lu and other merfolk from the deadly sunlight, an act that symbolizes a new era of understanding and harmony between humans and the sea. His notable ability, aside from his skill as an umbrella maker, is his knowledge of the town's history and the practical craft that ultimately becomes a key tool for protection and peace.