There is a break in the story of both the manga and the anime that fans will be familiar with: chapter 15 ("The Fish Gaze") in the manga and episode 12 ("One eyed fish") in the anime. In it, the "youth" of Ginko is shown, and the origin of his missing eye and white hair is explained.
One thing which has bugged me a bit is the ominous prophecy attached to it. Nui, Ginko's de facto mentor/rescuer tells him that the fish in a local pond (and she herself) only have one eye since they got exposed too much to the silver light created by a very powerful mushi, which she calls Ginko (a huge, silver fish). Nui notes that those who lose both eyes to it get turned into a mushi themselves, called Tokoyami. Nui also mentions that she performed experiments on fish that had already lost an eye, which showed that once they had lost an eye, they would invariably lose the other and turn into Tokoyami, even if they were never exposed to the silver light again.
Later in the story, Ginko (the main character, not the Mushi) loses an eye as well. Does this mean that Ginko's death is certain and unavoidable?