Yahagi is a Mushishi who discovered the larval form of Kagebi, thinking it was a new species of Mushi.

During the episode, Yahagi sees the weeds and decides to get rid of them by setting the whole mountain on fire, ignoring Ginko's advice. By doing so, she unleashes the Kagebi, and swallows one by accident in the confusion. She begins coughing up Kagebi weeds, and believes she will die. However, Ginko gives her a partial cure, allowing her to live on.