On a night-time 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. 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.