In 1929, he succeeded in having an historical novel, Yui Kongen Taisakki, serialized in a weekly magazine, and a similar historical novel about the Satsuma Rebellion, Nangoku Taiheiki, serialized in a newspaper following year. The success of these established him firmly as a writer of popular fiction.
Naoki had a reputation for being eccentric, as evidenced by his choice of a pen-name, which he changed four times between ages 31 and 35 to match his age that particular year (skipping over 34, as four was an unlucky number according to Japanese superstition). When he reached age 35 (Sanjūgo), he decided to keep the same name from that point onwards.
As well as historical novels such as Araki Mataemon and Odoriko Gyojoki, Naoki also wrote biographies of historical figures, including Kusunoki Masashige, Ashikaga Takauji, and Genkuro Yoshitsune, as well as contemporary social fiction, including Nihon no Senritsu ("Japan Shudders"), and Hikari: Tsumi to Tomoni ("Light: With Crime"). His historical novel Mito Komon Kaikokuki was the basis of a movie, followed by the extremely long-running television series Mito Komon, which remains popular to this day, and which is largely responsible for turning the historical Tokugawa Mitsukuni into a folk hero.
Naoki died in 1934 at the age of 43 from an acute case of Japanese Encephalitis. His grave is located at the temple of Chosho-ji in Kanazawa ward, Yokohama.