Izaya is an elderly woman who resides on Asuka Island, where she serves as the grandmother of Maya. Her physical appearance is that of a stooped, hunchbacked figure with a short stature, though she is actually quite tall when she stands up straight. She has pink hair tied in side locks with blue bands, her face marked by many wrinkles, and she often squints her eyes. Her typical attire consists of an elaborate orange ceremonial robe worn over a red shirt, complemented by numerous pieces of jewelry hanging around her neck. She carries a long, crooked walking staff.

On the surface, Izaya appears to be a stoic and stern woman, frequently wearing a grim expression, particularly when interacting with the Straw Hat Pirates. However, this exterior masks a deeply caring and compassionate nature. Her primary concern is the well-being of her granddaughter, Maya, and she is visibly distressed at the thought of Maya sacrificing herself to seal away the cursed sword known as the Shichiseiken. Izaya is also deeply worried about Saga, a young man from her community who has fallen under the malevolent influence of the sword, and she feels great relief when he is finally freed from its control. Her distinct style of laughter is expressed as "Ushashasha".

Within the story, Izaya acts as a guardian of tradition and keeper of knowledge on Asuka Island. She is responsible for protecting the village's ancient orbs and understands the ritual needed to seal the Shichiseiken. She holds a position of respect within her community, having once led the villagers to safety during a pirate attack. Her role becomes central when the cursed sword's power threatens the island. Izaya explains the legend of the Red Moon and the history of the Shichiseiken to the Straw Hat crew, detailing that the only way to create the seal is with the sacred orbs, which have been stolen. She initially demands that the pirates leave the island for their own safety, demonstrating her belief that all lives, whether pirate or civilian, matter. As the crisis escalates, she braces herself for the worst but ultimately witnesses the sword's destruction and the salvation of her people.

Izaya shares several key relationships that define her actions. Her most significant bond is with her granddaughter, Maya. Izaya tries to comfort Maya and is adamantly opposed to the young woman's decision to offer her own life to seal the sword, insisting that their family's destiny to protect the orbs should not require such a sacrifice. She also has a long-standing connection to Lacos, a village leader, and she offers him comfort by insisting that no one is to blame for the tragedies that have befallen Saga. Her relationship with the Straw Hat Pirates evolves from initial suspicion and stern demands for them to leave to a grudging appreciation for their help, especially when Monkey D. Luffy retrieves the stolen orbs, removing the need for Maya's sacrifice.

Throughout the movie, Izaya demonstrates notable abilities rooted in her position as the village elder. She possesses extensive knowledge of the island's history, the legend of the Shichiseiken, and the specific rituals required to combat it. She is able to complete the story of the Red Moon from an ancient carving when the text becomes illegible. Furthermore, she understands the mechanics of the sealing ritual, explaining how the orbs must be placed at specific locations to create a protective barrier over the island. Her wisdom and understanding of the sword's power prove crucial in guiding the other characters toward a resolution.