Yuki Kotonomiya is a central character in the visual novel and anime series 'Suigetsu.' She is a mysterious young girl with a serene and calm demeanor, often seen near bodies of water, which plays into the series' water-themed motifs. Yuki is pivotal to the unfolding narrative, as her past and connection to the protagonist drive much of the story's emotional and dramatic tension. Her interactions reveal deeper themes of memory, love, and the passage of time, making her a linchpin in understanding the series' overarching plot and emotional depth.