Hideo Suzuki, a 35-year-old man plagued by insecurity, is compelled to work as an assistant to a mangaka after his own series flops due to poor sales. While enduring a monotonous existence marred by hallucinations, he begins to doubt the quality of his relationship with his girlfriend, suspecting she might be having an affair with her ex-boyfriend. Although he confronts her regarding this potential infidelity, Hideo subsequently feels remorseful about his interrogation and resolves to go to her home to apologize. However, the world he knows is on the verge of being upended. Initially, nothing appears to have changed, but he quickly discerns that society has devolved into a living nightmare, as the terrifying truth of the events unfolding around him gradually dawns on him.