This novel (inspired by Dazai’s autobiography and written in the first person) tells the story of one person who feels since childhood utterly alien from his fellow human beings but learn to put a face to hide his deep sense of alienation and his despise for the hypocrisy of society. He feels incapable to belong to a human society (hence the title). Follows a descent into alcohol, drugs, suicide as the main character enters into aldulthood.
The story did remind me a little of Camus’ The stranger (l’etranger) in so far as both are a tale of a person alienated from the society at large. But Dazai also explore the sense of self-loathing and self-destruction and is therefore much darker (Camus sounds cheerful in comparison).
Dazai is known as a dark post-war writer and indeed this is a dark novel.