Raina is the narrator and protagonist of Guts and the author and illustrator of the book, which is largely a true story drawn from her experiences when she was 10 years old. She is an upper elementary student in a San Francisco Bay area community. She has a sister, Amara, who is five years younger, and a toddler brother, Will. The family, including her mother and father—and her grandmother for six months of the narrative—lives in a small two-bedroom, two-story apartment where Raina shares a bedroom with her siblings.

Much of Raina’s life centers on elementary school and her relationships there. She has several girlfriends, though her interactions with boys in her class are minimal. Her best friend is Jane, with whom she frequently has playdates and sleepovers. Her other close friends are a Black girl named Dina and a white girl named Nicole. Raina’s antagonist is tall, pretty Michelle, a Black girl who constantly teases and mocks Raina.

As the narrative develops, readers recognize that Raina faces two distinct personal problems, each exacerbating the other. She has IBS and a panic disorder. When she has a panic attack, it causes her to become nauseous.