Їнь

A member of Hei's team, an emotionless spirit medium known as a "Doll." Her power lies in tracking and observation through direct contact with water. Huang mentions that her "program" is a minimal one, incapable of showing emotion or even allowing her to make decisions for herself; however, she later debunks this by making the decision to keep working with Hei and the others when given the choice of leaving, a possible sign of her recovering her humanity.

Yin is of Finnish origin and her real name is Kirsi. She was once a student of a famed Finnish pianist named Eelis Kastinen, who slowly started developing a love interest in her mother. Yin's father died in a plane crash.