[1][2][3] The story centers on an aristocratic family in decline and crisis during the early years after World War II.

Twenty-nine-year-old Kazuko, her brother Naoji, and their widowed mother are members of an impoverished aristocratic family living in post-war Tokyo.

Kazuko and her mother move to the Izu peninsula countryside with the help of a relative, and she begins working in the fields to support them, claiming to be growing into a "coarse woman".

Kazuko finds Naoji's "Moonflower Journal," in which he rants about people's bigotry and insincerity, and writes about his addiction and his struggles as a writer and individual.

She repeatedly refers to ideas of Christianity and Marxism, having read a book by Rosa Luxemburg which she found in her brother's belongings, and dedicates the letters to "M.C.

Shortly after, Naoji dies by suicide, leaving behind a letter to his sister which gives his feelings of weakness over his aristocratic descent as the reason, also denouncing all ideologies which suppress the individual.

The Setting Sun first appeared in serialised form in Shinchō magazine between July and October 1947, before being published as a book the same year.