Shinra, a boy living in a forest with mysterious powers, calls for Ginko, The Mushishi, to help him with his problems. While Ginko is staying with Shinra, he tells him all about Mushi and his powers. Later on, while walking in Shinra's house at night, Ginko finds a Mushi... But this isn't an ordinary Mushi, it's Shinra's grandmother!

It is spring, and Ginko is taking a boat through a river, when the boat's boy, Kaji, asks Ginko whether he could help his mother, who's forgetting things and can't sleep. At first glance it may appear to be progressive amnesia, however something isn't right.

Ginko arrives at a secluded place, to meet an old acquaintance, who seems to be in charge of a large volume of archival, confidential text. Ginko is allowed to read it, and discovers it is the work of Tan'yu, a writer. Tan'yu is the descendant of the Karibusa family, being born with a black mark on a part of their body.