Yin, also known as Silver, is a quiet and emotionally reserved Doll in Darker than Black: Kuro no Keiyakusha. She serves as a surveillance and information-gathering operative for the Syndicate, typically acting through water or reflective surfaces. Yin travels with Hei and becomes one of the most important figures in his story, gradually showing signs of independence and deeper feeling despite her controlled existence. Her role is central to the series’ emotional core and to the mystery surrounding the Contractors and Dolls.