Ginko once passed through a town where a man was having prophetic dreams.  He gives the man medicine in order to stop them since they are caused by mushi.  He returns about a year later to find the town nearly destroyed.  He learns that the man did not take the medicine as he was instructed and that the mushi investing him had caused his dreams to become reality, killing nearly everyone.  Now he must try to find the pathway that the mushi take between the dream world and reality in order to put a stop to their involvement.