Morning Girl is a coming-of-age story for both protagonists, Morning Girl and Star Boy. As they grow up, both siblings grapple with questions of identity, each on their own journey of self-discovery. The search for identity is central to their experiences, reflecting the universal challenges of growing up.

Though the story never mentions her exact age, Morning Girl is likely on the cusp of adolescence. As such, she begins to confront her evolving identity. As she watches her younger brother impulsively throwing himself on the food during the feast, she reflects on the age gap between them: “I only wish I could join Star Boy now.” She acknowledges that while she is not yet a woman, she is “no longer a child” (49). Morning Girl’s search for identity also extends to her appearance. In Chapter 5, she realizes that she doesn’t have a clear image of what she looks like and turns to her mother for answers, asking if her face is long or round and what her eyes look like. Her concern with her physical appearance is typical of adolescence. She compares parts of her body to elements of the natural world: her chin resembles a starfish, and her brows are like clouds.