Shikoku refers to the 4 provinces which made up the island. But the title for this is a play on words. koku means country, land (so on), Shi meaning 4 as well as death. The title is the "death land" one, but it takes place in Shikoku.
Mistagged maybe? The novelist is generally considered a horror writer but this is more supernatural/fantasy, maybe thriller or mystery, but not even that quite. It is a good story. I would like to read the book. I could tell it was a novel