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 Nishikawa's personal entanglements become 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 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.