Nao Kashiwagi is a supporting character in the story, known primarily as the close friend and classmate of Tsubaki Sawabe. She is a student at the same middle school and also serves as the pitcher for the school's softball team. Her background is not heavily detailed, but she is established as a long-time companion to Tsubaki, often seen at her side during school hours and casual moments.

Her personality is marked by a direct and often blunt manner of speaking. She consistently tries to show Tsubaki the truth of situations in the most straightforward way, which frequently embarrasses Tsubaki or provokes a reaction. Despite her often inscrutable or indifferent facial expression, and a demeanor that can seem detached from others' troubles, her actions reveal a genuine care for the people around her. She possesses a sharp insight, especially into Tsubaki's emotional state, and she is known for her distinctive taste in romance media.

Her primary motivation is to help her friend Tsubaki confront her own feelings honestly. She recognizes that Tsubaki is stubborn about admitting her romantic feelings for Kousei Arima, and her direct advice and provocations are intended to break through that stubbornness and encourage Tsubaki to face the truth. This supportive, albeit provocative, role is her main function in the narrative.

Nao Kashiwagi's role in the story is that of a catalyst for Tsubaki's emotional development. She does not drive the main plot but serves as a grounded, perceptive presence who pushes Tsubaki toward self-awareness regarding her relationship with Kousei. Her interactions provide moments of levity and realistic friendship dynamics between the more intense musical and emotional arcs.

Her key relationship is with Tsubaki Sawabe. Their friendship is characterized by affectionate camaraderie mixed with playful provocation. Nao's blunt commentary often creates friction, but it is clear that she cares deeply about Tsubaki and wants her to be honest with herself. She has no significant direct relationship with Kousei Arima or Kaori Miyazono, as her influence is channeled entirely through her connection to Tsubaki.

In terms of development, Nao remains a consistent character throughout the series. She does not undergo a major personal transformation herself, but her persistent honesty and supportive role help facilitate growth in Tsubaki. Her presence underscores the importance of having friends who are willing to speak hard truths.

Her notable abilities are not musical or physical in a showy sense, but rather social and perceptive. She has a keen emotional intelligence that allows her to read Tsubaki's feelings accurately, and she possesses the confidence to speak bluntly even when it might cause embarrassment or conflict. As a softball pitcher, she also demonstrates athletic ability, though this is a minor aspect of her character. Her primary skill is her ability to act as a grounding, honest friend who refuses to let Tsubaki hide from her own emotions.