Rui's mother is a doctor who runs the only clinic on the small island where her family lives. She is a capable and dedicated physician, respected by the community for her work. Her primary motivation throughout the story stems from her desire to see her son, Rui, follow in her footsteps and eventually take over the family medical practice. This expectation places considerable pressure on Rui, as she encourages him to study hard and prepare for a career in medicine.

In the narrative, Rui's mother serves as a significant figure in his home life, representing the familial obligations and traditional path that he is expected to accept. While she is not a central character, her presence is felt through Rui's internal conflict between his duty to his family and his personal passion for music. Their relationship is characterized by a caring but firm dynamic; she believes she is guiding him toward a stable and honorable future, unaware of the depth of his musical aspirations. Over the course of the film, Rui's growing involvement with the band and his friendship with Totsuko and Kimi force him to confront his mother's expectations, making her an important catalyst for his character development. She does not undergo significant change herself, but her role as a supportive yet traditional parent highlights the generational and personal tensions that the young protagonists must navigate.