After the university Sone entered the foreign service and served in France and China. Since 1944 he had held several executive positions. Subsequently, he quit the Foreign Office after a clash of opinion with the then Prime Minister Shigeru Yoshida. He ran from the Kanagawa Prefectural constituency for the June, 1950, House of Councilors election, and was returned to the Upper House.
He married Haruko, who was the eldest daughter of industrialist Keita Goto.