No Longer Human is Dazai’s last and most important book. It is regarded as the most outstanding example of Japanese autobiographical fiction, or shishosetsu (“I novel”). A concern for the author and his or her personal revelations has a long history in Japan, going back to the female diary literature of the 800’s and 900’s. The “I novel” itself, which appeared in the 1920’s, was not only a recounting of events in the author’s life but also a merciless expose in the style of a confession, with the emphasis on fact, not fiction or art. Dazai took this form and stretched it by placing far more emphasis on art. He suppressed some facts of his life, rearranged others, and paid far more attention to the demands of narrative than did previous “I novel” writers.

In the 1940’s and after his death in the 1950’s, Dazai was the most popular writer in Japan, especially among younger people. First with The Setting Sun and then with No Longer Human, he chronicled Japan’s postwar atmosphere of degradation, despair, and nihilism, especially among those who had lost their money and their place in society. A new term entered the Japanese language based on Dazai’s fiction, the “setting sun tribe,” describing those people who scarcely felt human.