After working in Tokyo as a coordinator and a lyricist for the radio programs about ten years, he married Reiko Oka, his college sweetheart and a medical doctor, in 1965, and moved to his wife's town of Kanazawa.

In 1965, Itsuki traveled with his wife to the Soviet Union and Scandinavia and published his novel Good-bye to Moscow Hoodlums (Japanese: さらばモスクワ愚連隊), for which he was awarded Shosetu Gendai magazine's new author prize.

From 1969-93, he wrote a novel series titled The Gate of Youth (Japanese: 青春の門) about the life of Shinsuke Ibuki in eight volumes, for the first of which he received the Eiji Yoshikawa Prize in 1976.

Starting in 1981, he studied the history of Buddhism as a special student at Ryukoku University, Kyoto, and in 2001 he published Tariki: Embracing Despair, Discovering Peace in English, which was awarded the Book of the Year prize in the spiritual department.

[3] His latest books include Shinran (Japanese: 親鸞) in three volumes (2014), which was serialized with illustrations by Akira Yamaguchi and won the 64th Mainichi Publishing Culture Award Special Prize in 2010.