Insecure 35-year-old Hideo Suzuki is forced to work as a mangaka's assistant when his own series fails due to low sales. As he struggles through a mundane life plagued by hallucinations, he comes to realize that his relationship with his girlfriend isn't that great, suspecting that she may be cheating on him with her ex-boyfriend. After confronting her about the possible affair, however, Hideo feels bad about his inquisition and decides to visit her house to apologize.
But the world as he knows is about to be overturned. At first, not much seems to have changed, but he soon realizes that society has become a living nightmare, as the horrifying reality of what is taking place around him finally begins to sink in.