Sakura Nanamine is a century-old supernatural entity bound to Kamome Academy, serving as an overarching antagonist aligned with Yugi Tsukasa and the Entity within him. She poses as a third-year high school student in the broadcasting club, maintaining a human disguise to interact with others despite her true ghostly nature. This ability stems from her contract with Tsukasa, though its exact mechanics remain unspecified. Her appearance features light green hair styled in an asymmetrical bob with short bangs, two braids extending from her crown to her ears, and long sections framing her face and chest. Notable traits include green eyes with yellow flecks, consistently half-closed eyelids giving a disinterested expression, and a signature red gem brooch worn on all outfits. She wears Kamome Academy's winter uniform with yellow stockings and brown stripes, and her doll-like beauty is noted by others. During the tea party arc, she dons a long black sparkling dress with bishop sleeves, a white cravat, and boots. In Chapter 103, she appears in a maid outfit for a class event, retaining her signature brooch and stockings. A gag in the spin-off "After-School Hanako-kun" depicts her temporarily transformed into a male body with a taller, muscular build and shorter hair, wearing a male uniform adjusted with her brooch. Sakura exhibits an aloof and emotionally detached personality, rarely displaying overt emotions beyond occasional smiles during her first meeting with Nene Yashiro or irritation toward Natsuhiko Hyuuga and Tsukasa. She detaches from the moral implications of supernatural affairs, likening Tsukasa to "little more than a cat" to cope with his disturbing actions. Despite genuine fondness for Nene—whom she identifies as a kindred spirit due to their shared bonds with supernaturals—she prioritizes Tsukasa's directives, leading her to manipulate or betray Nene when required. This duality surfaces during the tea party arc, where she hospitably bonds with Nene over shared experiences while secretly confining her under Tsukasa's orders. Her core motivation revolves around an unspecified wish pursued for over a century, heavily implied to involve escaping Kamome Academy's confines. This wish forms the basis of her contract with Tsukasa, though its exact terms and the nature of her entrapment remain undisclosed. She died around 1901, evidenced by her admiration for Fukuzawa Yukichi, and her winter uniform and vulnerability to cold weather suggest a possible winter death. As a ghost, she holds significant authority, appointed as the overseer of the Seven Mysteries by Akane Sumire, though this role's impact on Hanako's leadership is unclear. Key story arcs highlight her strategic actions. In the tea party arc, she orchestrates Nene's capture, feigning camaraderie before immobilizing her for Tsukasa's plans. Later, she reveals the gruesome fate of Sumire—a victim of Hakubo (Mystery No. 6)—to Nene, intensifying Nene's guilt over destroying yorishiro and demonstrating Sakura's willingness to leverage psychological manipulation. Her dynamic with Tsukasa and Natsuhiko involves reluctant collaboration; she tolerates their antics but frequently expresses annoyance, particularly toward Natsuhiko's behavior. Trivia notes include her favorite snack (rakugan) and her name's meaning: "Nanamine" (七峰) incorporates the character for "seven," while "Sakura" (桜) means "cherry blossom."