[1] He was a prominent figure in radical politics in Japan, opposing the Russo-Japanese War by founding the Heimin-sha group and its associated newspaper, Heimin Shinbun.

Due to disregard for state press laws, the newspaper ceased publication in January 1905, and Kōtoku served five months in prison from February to July 1905.

He subsequently left for the United States, spending November 1905 until June 1906 largely in California, and he came into contact with other prominent anarchist figures such as Peter Kropotkin.

[2] Tosa was a hotbed of resistance largely due to the discontent of samurais, whose power was declining, and Kōtoku became at a young age an ardent supporter of the pro-democracy Liberal Party.

There he involved himself in public agitation, driven by the Liberal Party, calling for the abolition of the unequal treaties signed between Japan and Western powers, alongside freedom of speech.

[9] In protest against this decision, in October 1903 Kōtoku was one of a number of journalists who resigned to found the Heimin-sha group,[11] alongside its associated anti-war Heimin Shinbun newspaper, which started publication in November.

[15] Before he left California, he founded a Social Revolutionary Party amongst Japanese-American immigrants, which quickly radicalised towards the use of terrorist tactics to bring about the anarchist revolution.

Kōtoku's new, more radical ideas clashed with the parliamentary tactics affirmed by the party, and he advocated for anarchist revolution through direct action rather than electoral strategy.

[18] Outside of party politics once more, Kōtoku worked with others to translate and publish Kropotkin's anarcho-communist book The Conquest of Bread, alongside an American anarcho-syndicalist pamphlet The Social General Strike.

[15] Despite being ideologically opposed to hierarchy, Kōtoku was seen as an 'authority' by many younger anarchists due to Japanese cultural norms, and he himself referred to Kropotkin as sensei (teacher).

[26] The trial and its fallout signalled the start of the 'winter period' (冬時代, fuyu jidai) of Japanese anarchism, in which left-wing organisations were tightly monitored and controlled, and militants and activists were tailed 24 hours a day by police.