His father, Matsujirō Eda, ran an udon and soba noodle manufacturing and wholesaling business and was also a minor political leader in the local branch of the Minseitō Party.

In 1955, the two halves of the JSP reunited, and in 1957, Eda became a member of the party's Central Executive Committee, as well as head of its Agricultural Bureau.

[4] The "structural reform" platform drew inspiration from the recently concluded Anpo protests against the U.S.-Japan Security Treaty, which had achieved massive size and forced the resignation of conservative prime minister Nobusuke Kishi.

Eda and his allies viewed these protests as having been an unalloyed success in having allowed the JSP to play a leading role in fomenting a mass movement.

Eda's "structural reform" platform called for a combination of parliamentary pressure tactics and Anpo-style extra-parliamentary mass movements that would gradually move Japan toward socialism by forcing the government into a series of piecemeal concessions.

[5] Above all, Eda and his fellow structural reformers hoped to broaden the base of the JSP beyond a hard core of labor unionists, leftist student activists, and Marxist intellectuals to encompass people from many walks of life, in order to dramatically increase the party's potential supporters at the polls.

In order to achieve his goal of broadening the base of the Japan Socialist Party, Eda sought to rebrand socialism using more straightforward language that would cut through complex Marxist jargon and offer a simple, optimistic vision to the Japanese people.

[8] In this speech, Eda famously proclaimed, Socialism must be defined in sunny and cheerful terms that are easily understandable to the masses.

The main four accomplishments that humankind has achieved so far are America's high standard of living, the Soviet Union's thoroughgoing social welfare system, England's parliamentary democracy, and Japan's peace constitution.

[9] In later years Eda ran numerous times for Chairman of the Japan Socialist Party, but was unsuccessful, although he did serve a second stint as Secretary General from 1968 to 1970.