Harumi Ukishima serves as a spirited counterpart to her older sister Kasumi, embodying a playful immaturity that contrasts sharply with Kasumi’s demeanor. She acts on impulse, delivering unfiltered remarks and mischievous taunts, often targeting Kasumi herself. Her teasing antics delight in flustering her sister, prompting scoldings about decorum. Though openly critical of Ryouji—a figure she begrudgingly credits for sporadic help—her concealed affections for him run deeper than her sharp words suggest. Sources differ on her appearance, alternately describing purple hair with matching eyes or blue locks paired with violet irises, all set against a pale complexion. Her youthful frame measures 88-60-86 cm, while her wardrobe shifts between relaxed yukatas, slippers, and eccentric ensembles like lab coats or swimwear. Her personality merges bold confidence and stubborn independence with flashes of naive vulnerability, underpinned by a defiant streak. Unapologetically indulged, she indulges in drinks and revels in testing boundaries. Within her family, she navigates dual roles as a mischievous younger sister and a university student embracing her independence, occasionally stepping into the part of an aunt.