Naoko Takakura is a music teacher and the vice principal of Shirahamazaka High School. She becomes the advisor of the school's choir club after the principal, the club's original advisor, is hospitalized following a bicycle accident. She was also responsible for the school's vocal club. Her background includes a deep personal history with music: she wrote the song Melody of the Heart and pursued a career in teaching because of her love for music. In her high school years, she was a close friend of Mahiru Sakai. Mahiru's death has had a lasting impact on Naoko, and she has struggled to move past that loss.

In personality, Naoko is stern, serious, and often harsh, especially toward the enthusiastic but somewhat scatterbrained Konatsu Miyamoto. She believes music should be treated with respect and not as a game, which puts her in conflict with Konatsu's lighthearted approach. Despite her strict exterior, her motivations are rooted in genuine passion for music and a desire to honor the seriousness of the discipline. Her role in the story is that of a mentor figure who initially seems like an obstacle to the students' goals but gradually reveals her deeper caring and vulnerability. Her key relationships include her difficult mentorship of Konatsu, her unresolved grief over Mahiru, and her later connection with Wakana Sakai, Mahiru's daughter, in whom Naoko begins to see echoes of her old friend. Through this relationship, Naoko starts to accept the past and offers guidance and support to Wakana. Over the course of the series, Naoko develops from a rigid, grieving figure into someone who can let go and encourage the next generation. Her notable abilities include composing music, teaching, and overseeing the musical aspects of the choir club.