Mia Winchell is the protagonist of A Mango-Shaped Space. She is 13 years old and is short with wavy brown hair. Mia is an ordinary 13-year-old girl, besides her synesthesia. At the beginning of her coming-of-age narrative, she is not yet ready to grow up, and Wendy Mass presents her as shying away from a vast array of elements that denote adolescence: She dreads eighth grade, prefers to run in the woods when she should be doing her homework, and does not want to have a period. She often argues with both of her siblings and is quite private. Nobody in her life knows about her colors, just like nobody knows how Mango got his name. Mia believes that her grandfather’s soul lives on in her cat, which is something else she has never shared with anyone. Mia’s coming-of-age traces her learning how to share and process these things.

Mia’s synesthesia is the central component of the novel and it drives her character development. Once Mia learns that she has synesthesia, she becomes almost obsessed with her diagnosis. After spending years believing that there was something wrong with her, she finally has a name for her experiences.