After Japan's defeat in World War II, Japanese people faced a series of consequences. These included extreme deprivation of material resources, the deaths of countless people, the destruction of cultural assets, the US occupation, moral collapse, and many survivors did not know how to go on. In this extreme situation, people lost the confidence to continue to survive, and became immersed in endless anguish and despair. Ango Sakaguchi published "Discourse on Decadence" (April 1946) and "The Idiot" (June 1946) in succession to prevent people from falling into decadent sentiments. The two works are thought to echo each other. This essay analyzes the relationship between the two works, and discusses the significance of "decadence" in "The Idiot".