Osamu Dazai (1909-1948-Japan-pen name for Shuji Tsushima) was born into a wealthy family. He lived a life of considerable dissipation funded by his family money. He studied French literature in college where he met Masuji Ibuse (author of Black Rain) who helped Dazai begin to get his writings published in literary journals. He was not drafted into WWII because he had tuberculous. No Longer Human is the second best selling Japanese novel of all time, behind Kororo by Natsume Soseki.
No Longer Human is largely narrated as if it were the note books of a man named Oba Yozo. The novel has strong autobiographical elements. Oba is virtually unable to relate to to other people in his real personality so he adopts the pose of a happy laughing all the time person. Inside he is deeply alienated from his wealthy father (and all of proper society) who is appalled by his degenerate life style centering around drinking and prostitutes His only seeming friend is man way below him in intellect, culture and family background who is kind of his guide to the darker side of life in Tokyo. Women find Oba very appealing. He learns how to seek out highly nurturing and supportive women that can see that he has the potential to be a great artist if he could shape his life in another direction. He cares nothing for them and exploits them to avoid working. He does get in very serious trouble at one point and luck and family money get him out of trouble. Oba is very intelligent and insightful. In time he does begin to pursue a marginally successful career of sorts as an artist. He knows very well there are lots of things wrong with himself but he cannot find any reason to work to rise above his problems. The novel is divided into three sections which cover sections of Oba's life several years apart. No Long Human is a brilliant account of the mind of a very alienated man who is a spectator at his own life. I will not convey the ending so as to avoid spoilers but is very well done and completely sound artistically. I recommend this book without reservation with the observation that it is a bit (ok quite a bit) grim. Given its extreme popularity (over 12 millions copies have been sold) I think anyone interested in the Japanese novel at some point needs to read No Longer Human