Sayuki Tokihara is a third-year high school student serving as president of the calligraphy club. She possesses long blackish-gray hair with bangs, typically accessorized with a red headband featuring a side ribbon bow, and large golden-yellow eyes. Her standard school uniform consists of a pink blazer layered over a white shirt with a red bow tie, a blue and purple plaid pleated skirt, thigh-high dark stockings, and brown loafers. She stands 172 cm tall and weighs 55 kg. Outwardly, she projects an image of a mature, playful upperclassman known for her kind demeanor, finding enjoyment in calligraphy and club activities. Despite this, she struggles significantly with cleanliness, habitually leaving the clubroom disorganized with ink spills and scattered papers. Her playful nature extends to mischievous pranks, including drawing on peers' faces or pressuring them into wearing costumes. This behavior connects directly to her concealed masochism, as she deliberately engineers situations hoping to provoke punishment. Her core personality centers on this secret masochistic fetish. She harbors an intense desire to be dominated, explicitly aspiring to become Keiki Kiryuu's pet. This fixation ignited after witnessing a dog-owner interaction, fueling envy and a craving for a master-pet dynamic with him. She openly wears a collar and lead symbolizing this fantasy, though Keiki consistently rebuffs her advances. Her masochism coexists with manipulative tendencies; she employs hidden cameras for blackmail and strategically engineers scenarios to force intimacy, such as licking him or arranging isolated encounters. Her background involves strict paternal pressure to excel in calligraphy, which curtailed her social development. Though initially joining the club due to this influence, she later confesses she values the club primarily for the camaraderie, especially with Keiki, more than calligraphy itself. This attachment fuels her desperation to recruit new members and prevent the club's disbandment. Relationships define key aspects of her character. With Keiki, her feelings evolve from playful teasing into intense romantic obsession. She exhibits jealousy over his interactions with other girls, particularly Yuika Koga and Ayano Fujimoto. A pivotal conflict erupts when Keiki mentions preferring the student council over her club, causing her to cry and temporarily avoid him. Despite reconciliation, he later confirms she was his first love but ultimately chooses another girl, deepening her emotional distress. Her rivalry with Yuika Koga is immediate and mutual, rooted in their opposing fetishes—Sayuki's masochism versus Yuika's sadism—and competition for Keiki's attention. They frequently trade insults, with Yuika labeling her a "witch." Sayuki's jealousy peaks concerning Ayano, leading to angry outbursts and emotional withdrawal when Keiki interacts with her. Character development reveals moments of vulnerability, like crying after Keiki's rejection, and unexpected assertiveness. For instance, she diverts club funds to purchase bunny costumes for members in an attempt to regain his attention. Her calligraphy skills prove practically useful, such as writing with ketchup during a cultural festival to rescue the club financially. Despite her heartbreak over Keiki's final choice, she persists in club activities, indicating gradual resilience.