On a nighttime walk along a Tokyo riverbank, a young man named Nishikawa stumbles on a dead body, beside which lies a gun. From the moment Nishikawa decides to take the gun, the world around him blurs. Knowing he possesses the weapon brings an intoxicating sense of purpose to his dull university life. But soon his personal entanglements become unexpectedly complicated. Through it all, he can’t stop thinking about the gun --- and the four bullets loaded in its chamber. As he spirals into obsession, his focus is consumed by one idea: that possessing the gun is no longer enough --- he must fire it.
A young writer is assigned a difficult task by his editor: he is to write an investigative biography of a death row inmate named Yudai Kiharazaka, a 35-year-old photographer who has been convicted of the murders of two women. Trying to unearth the truth about Kiharazaka forces the writer to grapple with horrifying archival material and to interview dangerous, grotesque people --- not least of all Kiharazaka himself.