Ayaka Usami is a supporting character who originates from Kyoto, where her family holds significant status as the proprietors of the Temple Hotel. She is introduced in the story as the arranged fiancée of the romance novelist Eiri Yuki, a betrothal orchestrated by their families that Eiri himself does not actively support. At the time of her first appearance, she is seventeen years old.

In terms of personality, Ayaka is depicted as a strong-willed, determined, and stubborn individual. Her primary motivation is her deep-seated love for Eiri Yuki, which compels her to run away from her home in Kyoto to Tokyo in order to find him. Upon discovering that Eiri is living with and developing a relationship with the aspiring musician Shuichi Shindo, she confronts Shuichi directly. She tells him to stay away from Yuki and slaps him, expressing her belief that a relationship between two men is wrong and that they will only hurt each other.

Despite her initial hostility, Ayaka's motivations are rooted in a genuine, if misguided, care for Yuki's well-being. She is aware that Yuki does not love her and that he would not be truly happy if he were to marry her. Her role in the narrative evolves from being an obstacle for the main couple to a figure who, out of love, chooses to step aside. When she realizes the depth of Shuichi's feelings, she ultimately backs off, recognizing that Shuichi is the one who can make Yuki happy.

Ayaka's key relationships are central to her character arc. Her relationship with Eiri Yuki is defined by her unrequited love and her role as his socially sanctioned fiancée. Her dynamic with Shuichi Shindo begins with intense rivalry and conflict but eventually leads to an understanding. This development paves the way for her most significant relationship in the story: with Hiroshi Nakano, Shuichi's best friend and bandmate. Hiroshi develops a crush on her, and after Ayaka lets go of her hopes for a future with Yuki, she agrees to start dating Hiroshi.

Throughout her time in the story, Ayaka demonstrates notable abilities of emotional resilience and personal strength. Her character development is marked by her transition from a determined pursuer of an unattainable love to a person capable of letting go. She shows a willingness to set aside her own desires for the sake of another person's happiness, managing to move forward with her life while maintaining a smile. She is a figure who, while initially an antagonist to the central romance, earns a degree of respect for her capacity to accept reality and find her own path.