Kenzō Matsumura was born on January 24, 1883, in Nishinami district, Fukumitsu, Toyama prefecture, the eldest son of a wealthy landowner who ran an apothecary shop.

[1] His biological mother left the family for unknown reasons when he was two years old and he was raised by his stepmother, alongside a half-brother and half-sister.

In 1942, he was reelected as a "recommended" candidate of the Imperial Rule Assistance Association, signaling his collaboration with the wartime one-party state that he would later name as one of his life's greatest regrets.

But Matsumura's collaboration was more than partial, as in 1944 he chaired the Imperial Rule Assistance Political Association's Policy Research Council, and in 1945 he was named its Secretary-General.

[3] During his time as a purged politician, Matsumura made pocket money by farming shiitake mushrooms and survived by gradually selling off the forest lands in Fukumitsu that he had inherited from his father.

[11] In the debate over who would succeed Ikeda as prime minister, Matsumura supported veteran party politician Ichirō Kōno, who favored dramatically increasing trade with China, whereas Miki broke ranks with Matsumura and supported Kishi's brother Eisaku Satō, an ex-bureaucrat who promised to maintain low levels of trade in accordance with US wishes.

Matsumura's lack of access to power led to defections from his ever-shrinking faction; his most loyal remaining lieutenants begged him to retire and step aside for a younger leader, but Matsumura refused, and his faction sank into irrelevance and eventually disappeared, while Miki's gained strength and eventually Miki would rise to become prime minister in 1974.

Matsumura died August 21, 1971, at the age of 88, just one year before seeing his long-held dream of China and Japan normalizing diplomatic and trade relations come to pass.

[13][14] As a result, for the first time in human history, a World Constituent Assembly convened to draft and adopt the Constitution for the Federation of Earth.