Haruka Hasebe attends Tokyo Metropolitan Advanced Nurturing High School in Class D. She has long blue hair, orange eyes, and a distinctive teardrop-shaped mole beneath her left eye. Her mature figure, including a notably large bust, often attracts unwanted male attention, making her self-conscious and reluctant to socialize, especially with flirtatious individuals. She typically wears her school uniform with the top button undone and her tie loosely fastened. Initially reserved and preferring solitude, Haruka avoids group activities, even skipping class swimming sessions. However, her personality shifts dramatically within her trusted Ayanokōji Group, where she becomes talkative, playful, and enjoys assigning affectionate nicknames like "Kiyopon" to Kiyotaka Ayanokōji to tease friends. She shows strong loyalty and protectiveness, particularly toward Airi Sakura, encouraging her to overcome shyness and confess romantic feelings. Later revelations show Haruka unconsciously enjoys feeling superior when helping weaker individuals like Airi, a trait causing interpersonal conflicts and stemming from familial influences that hindered genuine friendships earlier. Her backstory includes an unrequited middle school crush on an athletic upperclassman she never pursued. In high school, witnessing Kiyotaka's physical prowess during a relay race sparks similar interest, leading her to test her feelings by spending time with him. Discovering Airi’s romantic attachment to Kiyotaka, Haruka suppresses her own emotions to support her friend, prioritizing their bond. Following Airi’s expulsion during a unanimous vote exam, Haruka undergoes intense development. Blaming Kiyotaka and Suzune Horikita, she seeks revenge, plotting with Akito Miyake to drop out and sabotage Class D’s academic points. She isolates herself, skips school for a week, and expresses open hostility. A pivotal confrontation occurs when Kiyotaka delivers a package from Airi containing a maid dress. Haruka initially interprets it as hatred, but Kikyō Kushida intervenes, revealing Airi’s new idol career and challenging Haruka’s self-serving narrative. This revelation, combined with Kikyō’s assertion that Haruka’s behavior mirrors her problematic family dynamics, forces Haruka to reconsider. She abandons her dropout plans, reconciles with her academic responsibilities, and participates as a maid in the class’s cultural festival café to honor Airi’s memory. Her relationships are defined by loyalty and conflict. She shares a deep, protective bond with Airi. Her dynamic with Kiyotaka evolves from playful teasing and hidden admiration to resentment post-expulsion, resulting in a permanent rift despite his role in delivering Airi’s gift. Akito Miyake remains a steadfast ally, supporting her emotionally during grief and revenge plans, with hints of his romantic feelings. She distrusts "perfect" individuals like Honami Ichinose, suspecting hidden flaws. Academically, she holds average ratings: C (52) in academics, C (52) in physical ability, C- (43) in thinking, and C (46) in social contribution.