On a nighttime walk along a Tokyo riverbank, a young man named Nishikawa stumbles on a dead body, besides which is lying a gun. From the moment Nishikawa makes the decision to take the gun, the world around him blurs. Knowing he possesses the gun brings an intoxicating sense of purpose to his dull university life. But Nishikawa's personal entanglements are becoming unexpectedly complicated: he finds himself romantically involved with two women, while his biological father, whom he's never met, lies dying in a hospital. Through it all, he can't stop thinking about the gun—and the four bullets preloaded 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.