Kozue Kuranaga serves as the class representative for the homeroom shared by Haruka Kasugano, Ryouhei Nakazato, Kazuha Migiwa, and Akira Amatsume, known as "Class Rep." She develops strong feelings for Haruka after a near-bicycle collision outside school, captivated by his gentle demeanor and appearance. Physically, Kozue has black hair and grey eyes, often styled in a ponytail or short pigtails, frequently wearing a hair pin on the left side. Her typical attire includes a white blouse and a brown skirt. Her appearance changes significantly by the conclusion of the anime and in the sequel *Haruka na Sora*, where she wears her hair untied, symbolizing a new beginning in Japanese culture and reflecting drastic life changes. Kozue's personality combines shyness, politeness, and a strong sense of responsibility, classifying her as a "dandere." Despite her reserved nature, she frequently indulges in vivid romantic fantasies about Haruka, termed "delusion mode," attracting teasing from classmates like Ryouhei. She dislikes rural life and aspires to move to the city upon gaining independence. Intellectually gifted but athletically challenged, she initially prioritizes rationality over emotion, though she later acknowledges the limitations of this approach. As class representative, she diligently performs duties like ensuring classroom security and managing administrative tasks, often staying late to verify locked doors and windows. Her initial interactions with Haruka involve assisting him with Sora’s school materials and expressing relief upon learning Sora is his sister. However, she later advises Haruka to moderate his public interactions with Sora due to spreading rumors. Kozue’s character development intensifies after witnessing Haruka and Sora’s intimate relationship. In the anime, she flees in shock and later confronts Haruka tearfully, declaring her love and vowing never to speak to him again—a statement she regrets. This trauma catalyzes her hairstyle change and prompts her to question Nao Yorihime about whether mutual feelings alone validate a romantic relationship. In the manga, Kozue appears more frequently, showing concern for Haruka’s well-being in Chapter 2, participating in group activities like a beach volleyball game in Chapter 7, and delivering school materials to Haruka’s home in Chapter 11, where she encounters Sora nude. After Sora implies her sexual relationship with Haruka in Chapter 12, Kozue runs away but later apologizes and joins the search for Sora when she disappears, affirming her friendship with both twins despite her confusion over their relationship. In *Haruka na Sora*, a sequel/fandisc to the original visual novel, Kozue receives her own romantic route where Haruka reciprocates her feelings, contrasting her unrequited love in other media. This route explores her character more comprehensively, including lighter, comedic elements. Kozue is the only major female character in the anime without explicit sexual content and one of two characters (alongside Yahiro Ifukube) without a dedicated arc in the anime adaptation.