Yin

Yin is a blind teenage Doll who supports Hei’s Syndicate team. She later flees from the Syndicate with Hei and begins to evolve. Yin is a slender small young woman with long grey hair, which she keeps tied back with a purple ribbon. She has purple irises. She wears a dark purple dress with black hem and a black top which covers her neck, shoulders and arms. Her outfit is completed by black leggings and black shoes. At first, Yin was portrayed a doll unable to show any emotion. Huang mentions that this is due to her "program" which was minimal and didn't allow her to make her own decisions. However, during the course of the series, Yin begins to display emotions and her own will, deciding to follow Hei and remain to be his partner, and even observes and notices a change in his behavior, despite not being ordered to do so. This has been made apparent when she called Hei from the void to come back to her and not leave her alone. In the process, her observation specter evolved or upgraded, now having a human-like body shaped with her silhouette and is capable of physical touch. She also seems to have feelings and affection for Hei, as commented by Amber. Which is then confirmed in Gaiden. Earlier in the story, Yin saw that Hei was helping a friend who had a doll and she just came to his apartment on her own accord which shocked Hei. She then showed that she really cared for the other doll as she urged Hei to assists in her silent pleas for help. Mao simply didn't understand this.