A boy named Yoki is found in the woods by a lady named Nui.  Nui learns that Yoki can see mushi.  She tells him that he can stay until his leg heals.  During his stay she teaches him about some of the mushi that he can see.  She also teaches him of the mushi in the pond that takes an eye from it's viewers, as it did with her's.  Yoki finds that the dark mushi is called the Tokoyami while the light mushi is called Ginko.