Haruka Minami is the eldest of the three Minami sisters and is a second-year student in high school. Her life is largely defined by her role as the primary caretaker for her younger siblings, Kana and Chiaki, a responsibility she has shouldered for many years. This has shaped her into the most reliable and responsible member of the household, with her days filled with cooking, cleaning, shopping, and other domestic tasks that keep the family home running smoothly. Despite her generally kind, nurturing, and calm demeanor, Haruka possesses a hidden domineering and formidable side. During her junior high school days, she was known as Banchou, a title for a gang leader, which stemmed from her ability to command the obedience of those around her with a single serious glare. This strength, however, is typically kept in reserve.

Her primary motivation stems from her deep love for her sisters, having effectively sacrificed much of her own childhood and personal freedom to raise them. As a result of these responsibilities, she does not participate in any school clubs, even though she is a superb volleyball player. She also unconditionally turns down all suitors without consideration. Her dedication has earned her immense respect from her sisters; the youngest, Chiaki, idolizes her as a perfect role model and addresses her with the highly respectful term nee-sama, using polite Japanese when speaking to her. While generally composed, Haruka is known to become extremely lazy when left alone by herself, suggesting she exerts significant willpower to maintain her motherly exterior. She is also prone to embarrassment and has a notable weakness in her terrible sense of direction.

Within the narrative, Haruka serves as the stable, mature center of the family, often acting as a bemused observer to the antics and conflicts perpetrated by Kana and Chiaki. She interacts closely with her two high school friends, Maki and Atsuko, but her primary world revolves around her home. Her relationships are key to her character. She guides Natsuki, a boy from another family with the same surname, who shows signs of affection for her. She has also unintentionally become the object of admiration for the eccentric volleyball club captain, Hosaka, though she remains largely unaware of his elaborate fantasies. Despite her formidable reputation and strength, she remains a caring figure who is dedicated to providing a stable and loving home for her sisters. Her academic performance is excellent, and she is an exceptional cook, as well as a remarkably skilled bubble gum bubble blower. In the specific OVA Minami-ke: Betsubara, her character continues to be displayed through small, everyday moments such as her happiness when Chiaki eats her vegetables, her discussions about meal planning with friends, and the typical chaotic misunderstandings of holidays like Valentine's Day within the Minami household.