Dr. Hiroko Yanagi practices medicine at an old Western-style hospital. She has black hair typically pulled into a ponytail, distinctive pink eyes, and wears glasses along with a cross necklace. Her work centers on studying patient Takumi, who gained unusual abilities after an accident: perceiving past events tied to hospital locations ("deep voices") and sometimes entering others' consciousness during sleep. Yanagi collaborates with Amano Aki to investigate the hospital's mysterious history, seeking to understand Takumi's powers and their link to the institution's past. The character appears in the 2002 *Deep Voice* light novel and its three-episode OAV adaptation.