Harumi Ukishima possesses striking purple hair and violet eyes, complemented by a notably large bust and pale skin. Her wardrobe features diverse outfits including miniskirts, tube tops, lab coats, bikinis, yukatas, and high-heeled shoes. As Kasumi’s younger sister, she exhibits an assertive, confident personality with rebellious tendencies. Her demeanor contrasts sharply with Kasumi’s, often appearing more childish and unrestrained. She routinely employs blunt, provocative language—especially toward her sister—prompting Kasumi’s appeals for greater decorum. She shares prior acquaintance with Ryoji, who occasionally assisted her with minor tasks. Despite this history, she openly mocks him with ironic criticism. These jabs mask complex, unrecognized romantic feelings rather than genuine dislike. In specific scenarios, she engages in social activities like drinking and navigates intimate dynamics, including entrapment or seduction situations.