He was born the second son of Tsuneichi Kinoshita in Miyuki, a village in the eastern part of Hiroshima Prefecture.
On 22 July 1920, his father was killed at work; on 3 August 1922, his mother married Tsuneichi's brother, Itsu, a pharmacist.
In 1932, Kinoshita began studying French literature at Waseda in Tokyo, but he was forced to switch to pharmacology in Nagoya in order to continue the family business, when his elder brother became a doctor.
Kinoshita disliked working as a pharmacist and is described by his family as a distant man who frequently undercharged his clients for the medicine he provided.
In July 1965, he wrote his last poem, "Gone So Long", commissioned by a newspaper for the 20th anniversary of the bombing of Hiroshima.