Deol is a minor character in Maquia: When the Promised Flower Blooms, serving as one of the first humans to offer kindness and shelter to the protagonist, Maquia. He is the younger son of Mido, a warm-hearted woman who runs Helm Ranch, a goat farm located in the village of Helm. Deol has an older brother named Lang, and the family also includes a dog named Onora.

In terms of the story's timeline, Deol is a child of a similar age to Maquia when she first arrives at the ranch with the infant Ariel. He lives a simple, rural life with his family, helping with the daily tasks of running the farm, which primarily involves raising goats to produce milk and cheese. His personality is not explored in great depth, but he is presented as a typical, boisterous young boy living in a lively household.

Deol’s primary role in the narrative is to be part of the stable and loving human family that provides Maquia with her first real home and a model of human parenthood. When Maquia, a lost and frightened young Iorph who knows nothing of the outside world, arrives carrying a baby, Mido immediately takes them in. Deol and his brother Lang thus become like siblings to Maquia as she learns to care for the child, Ariel, on their farm. This period at the Helm Ranch represents a fleeting but crucial chapter of peace and normalcy in Maquia's much longer life. The relationship between Maquia and the family, including Deol, helps ground her and gives her a foundation for raising Ariel.

Deol does not have any notable special abilities, as he is a normal human child. His development within the film is not a focus, as the story's perspective remains with the ageless Maquia. Consequently, the audience does not follow Deol into his adulthood; his significance is contained within the early, formative years of Maquia's journey into the human world.