No Longer Human (人間失格, Ningen Shikkaku) is a Japanese novel by Osamu Dazai. Published after "Run Melos" and "The Setting Sun", "No Longer Human" is considered Dazai's masterpiece and ranks as the second-best selling novel in Japan, behind Kokoro.
This novel, despite being serialized as a work of fiction in 1948, is narrated in the first person and contains several elements which betray an autobiographical basis, such as suicide—a recurring theme in the author's life. Many also believe the book to have been his will, as he took his own life shortly after the last part of the book (it was serialized) was published, in June 13, 1948. This is not accurate, though, as he had started work on it long before.
"No Longer Human" paints the portrait of the life of Ōba Yōzō (大庭葉蔵?), a troubled soul incapable of revealing his true self to others and who is instead forced to uphold a facade of hollow jocularity. The name of the main character, Ōba, is actually taken from one of Dazai's early works, "Petals of Buffoonery" (道化の華?).
Ōba refers to himself throughout the book using the reflexive pronoun "Jibun" (自分), whereas the personal pronoun "Watashi" (私) is used both in the foreword and afterword to the book by the writer, whose name is unclear.
Dazai might have been a sufferer of Complex post-traumatic stress disorder whilst writing the book. Mike Lew has praised the book for expressing male sexual trauma.
+thank you very much to my kouhai for this:
Synopsis for Mashi Senpai