How are "ghosts" important in the book, Ghosts of the Tsunami?

Ghosts, according to Japanese tradition, are the spirits of dead people who can, at times, possess the bodies of the living in order to relay messages or express emotions. Parry mentions ghosts frequently, as do the people he speaks to in the aftermath of the tsunami. Reverend Taio Kaneta, a priest living inland at the time of the disaster, explains that he saw many more people than usual come to him for help with possessions since it appears that the number of reported ghost sightings increased after such a huge number of deaths. The Japanese belief in ghosts forms part of the worldview of this country and its citizens, thus it cannot be dismissed and is treated as a highly important phenomenon by the author himself.