Setsuna Kiyoura is a petite 16-year-old student in Class 1-3 at Sakakino High School, serving as the female class representative and student council member. Standing 142cm tall with black hair often tied by a ribbon, red eyes, and measurements of 74-54-76, her small stature frequently causes others to mistake her for a junior high student, a point of self-consciousness. Born February 14, 1988, she is the daughter of Mai Kiyoura and Shun Hazama, aware of Shun as her father unlike her half-siblings Sekai Saionji, Inori Ashikaga, and Roka Kitsuregawa. This family connection makes Makoto Itou her uncle. She grew up in Motehara alongside Sekai and Niki Ookuma, though she and Sekai later distanced themselves from Niki. Setsuna maintains a stoic, impassive, and taciturn exterior, speaking with minimal emotion. However, she possesses a deep protective instinct toward Sekai, prioritizing Sekai's well-being above her own feelings. This devotion drives her to take actions intended to secure Sekai's happiness, such as attempting to eliminate romantic rivals like Kotonoha Katsura from Makoto's life, without personal malice toward them. Her emotional vulnerability surfaces rarely, typically when intoxicated or in private moments with Makoto, and she occasionally displays subtle expressions like a light smirk or a V-sign. A traumatic childhood experience involving a friend's death from illness fuels a heightened concern for others facing sickness. In "School Days," Setsuna harbors a longstanding crush on Makoto Itou, stemming from him defending her from bullies during the entrance ceremony and encouraging her to become class representative. She initially suppressed her feelings to prioritize Sekai's relationship with Makoto. During school festival preparations, after comforting Makoto as he confides his romantic confusion, she confesses her love but asks him to keep it secret and forget it for Sekai's sake. Depending on choices, this encounter can result in her pregnancy, leading to a scene where she confronts Makoto's mother, declaring herself his wife. Setsuna subsequently transfers to Paris to remove herself from the love triangle, though the timing and occurrence vary. In the anime adaptation, she pressures Makoto to remain devoted to Sekai before leaving for France, even sleeping with him to reinforce this goal, a plan which ultimately fails. "Summer Days" and "Shiny Days" feature Setsuna as the protagonist during summer vacation. When Sekai contracts mumps, Setsuna temporarily takes over her shift at the Radish family restaurant. Though initially disliking the job, she continues after encountering Makoto, who invites her to spend time together after shifts. In "Shiny Days," an incident occurs where Setsuna accidentally douses Inori Ashikaga with water and later inadvertently exposes herself due to Inori's panic, leading Setsuna to knock Inori unconscious in retaliation. During a hot springs trip with classmates in the OVA "Valentine Days," Setsuna bluntly interjects a discussion about breast sizes involving Kotonoha by stating, "it's not the size, but the satisfaction," shocking the others.