The Setting Sun (1947) is a very important work in the post-war literary world of Japan, and it has created a record of the best selling of post-war literary works. The word "setting sun clan" is widely known as the pronoun of the declining aristocrat.The works show the declining social status of the aristocratic descendants and the embarrassment of the disappeared high position and great wealth after the war, and the book can be said as an elegy of Dazai Osamu to the declining aristocrat.No Longer Human (1948) is the most outstanding literary work of Dazai Osamu, written before his suicide, that is, his last masterpiece.It is also "the most profound point of arrival" of Dazai Osamu literature (Okuno, Takeo).It portrayed a perverse young intellectual who suffered from the inconstancy of the world and addicted to wines, and finally destroyed himself.