He was forced to support himself through college, attending the Kokugakuin University. After graduation, he went to work for the publishing company, Kawade Shobo, but that company went bankrupt a couple of years later. The advertising campaign he mounted popularized Hawaii as a tourist destination as well as promoting Suntory whiskey.
Yamaguchi's true literary career started in 1954, when he began contributing works to the magazine of literary criticism, Gendai Hyoron ("Contemporary Criticism"). This story about an average white-collar worker in Tokyo set the tone for many of his future works, which mock the new affluence of urban society in the 1960s, in contrast to the bitter war and post-war period. Other noted works are: Majime ningen ("A Serious Person"), Izakaya Choji, Ketsu zoku ("Blood Relations"), Kazoku (Family) and Waga machi ("Our Town").
Nanjamonja is a humorous account of travels around Japan. Yamaguchi also wrote a biography on Yoshino Hideo, in which he describes his own experiences during the period he lived in Kamakura, in the house next door to Kawabata Yasunari from 1945-1948. Yamaguchi died in 1995.
His grave is in Uraga, Kanagawa.