Hiyori Nishiyama is a 15-year-old high school student. A traumatic car accident on her first day of middle school caused multiple bone fractures and required extensive hospitalization, preventing her from attending school for nearly a year. This prolonged absence fostered significant social anxiety and fear of peer rejection, making her reluctant to return even after physical recovery. Her mother eventually compelled her to reenter school as a freshman. Physically, Hiyori stands at 140-142 centimeters, making her the smallest student in her class and leading to mistaken assumptions she is a middle schooler. She has large brown eyes and shoulder-length hair, described as either brown or blonde. Classmates often describe her appearance as cute, emphasizing her small size. Yuushin Hirose nicknamed her "Hiyorin" due to her chick-like smallness and vulnerability. Hiyori's personality is defined by extreme shyness and social apprehension rooted in fear of ridicule. She tends to cry or flee from embarrassing situations, like accidentally exposing her underwear while rushing to clean the chalkboard – an incident causing her significant distress. This shyness manifests as reluctance to speak in class or initiate interactions. She harbors deep-seated insecurities about her height and social capabilities, contrasting herself with peers who make friends easily. Yet she demonstrates underlying kindness, empathy, and a growing capacity for courage when supporting others. Her primary relationship is with childhood friend Ritsuka Nakano, known since kindergarten. Ritsuka acts as a protective figure and emotional anchor, encouraging Hiyori's social reintegration. Hiyori's most significant development occurs through interactions with Yuushin Hirose, a 190-centimeter-tall classmate whose outgoing nature contrasts her introversion; their 50-centimeter height difference becomes a recurring point of attention. After Yuushin comforts her following the underwear incident, Hiyori gradually develops romantic feelings for him, admiring his social ease. She confesses during a fireworks festival, and after initial interruptions, they begin dating. Their relationship navigates challenges including Hiyori's self-esteem issues and external romantic rivals like Kisaki Tominaga (Yuushin's childhood friend) and Reina Matsushima (a transfer student). Hiyori's social circle expands to include classmates like Natsuki Aizawa, who finds her extremely cute and becomes protective, and Kou Nitobe, a shy classmate with whom she initially has a rocky relationship due to mutual misunderstandings. Kou later develops unrequited feelings, confessing, which she gently rejects. She also cares for a stray cat named Pui-pui, found by Yuushin on school grounds, though the cat shows stronger attachment to Yuushin. Her homeroom teacher, Miyoko Mitani, provides comic relief through her own romantic struggles. Hiyori exhibits measurable growth in confidence and social ability. She progresses from hiding behind Ritsuka to actively participating in class activities, forming multiple friendships, and assertively navigating romantic challenges. Key milestones include performing a maid café duty during the school festival despite embarrassment, confronting jealousy in her friendship with Ritsuka, and mediating conflicts between friends. Her development reflects a gradual overcoming of trauma-induced social anxiety through persistent effort and supportive relationships.