His father's work required frequent changes of residence, so Dan grew up with his grandparents in Yanagawa from age 6 onwards.

His parents were divorced when Dan was nine, and he subsequently moved to live with his father in Ashikaga, Tochigi Prefecture, where he led a solitary life, walking over hills and fields.

After graduation, Dan dedicated himself entirely to writing, and in 1944 won the Noma Prize while serving as a newspaper war correspondent.

During his career, he wrote novels and poetry, and traveled extensively in Japan, Europe, the United States, China, Russia, Australia and New Zealand.

He lived in Santa Cruz on the seacoast west of Torres Vedras, Portugal, from 1971 to 1972 in a house on a street that now bears his name, Rua Professor Kazuo Dan, Nº 6.