Cai’s manifesto appeared at a moment of crisis for the Taiwanese anticolonial movement. Begun in 1914 by liberal elites seeking full assimilation of Taiwan into Japan, by 1928 the movement had split into a radical, Marxist wing and an increasingly ostracized moderate wing, of which Cai was a prominent representative. One way to interpret the significance of Nihon honkokumin ni atau is as an attempt to garner support for the liberal wing of the movement.

The liberal wing of the Taiwanese anticolonial movement went through three distinct phases. The movement began with a demand for assimilation into the metropole. In the early 1920s, this morphed into a demand for self rule. The failure of the movement to achieve its goals led to its marginalization in the 1930s and the rise of Marxist activists to prominence.

Cai first became involved in the movement as a member of the Assimilation Society (Dōkakai). The Society sought to promote “harmonious relations between Japanese and Formosans based on the concept of racial equality” (Chen 1972, 479, quoting Article 3 of the association's charter in Nihon tōjika no minzoku undō II, 17-18). The Society objected to the discrimination in education, law, and customs that the Government General imposed on Taiwanese people. Arguing that the Government General's insistence on cultural assimilation first and equality second was counterproductive, the Society proposed assimilation as an institutional matter: first, equalize colonial Taiwanese institutions with their metropolitan counterparts, then Taiwanese people will become willing and productive subjects of the empire. In practice, the Society's concept of assimilation also promoted a sense of Taiwan's geopolitical uniqueness. On the one hand, Taiwan was to be considered fully a part of Japan and Taiwanese people equal to Japanese people. On the other, Taiwan was to be treated as a unique place, a special kind of bridge between Japan and China.

It’s possible to see the contours of this ambiguity in the speeches that Itagaki Taisuke gave as the president of the society. Itagaki was a liberal member of parliament, well known as a leader of the Freedom and Popular Rights Movement and the founder of the Liberal Party. In 1914, Lin Hsien-t’ang, the Society’s founder, invited Itagaki to travel to Taiwan to serve as the society’s first president. While in Taiwan, Itagaki gave three speeches, each of which advocated for the “assimilation” (dōka) of Taiwan into the metropole.

Itagaki described assimilation as a process of expanding the cultural and political boundaries of Japan to fully incorporate Taiwan. Itagaki argued for the complete absorption of Taiwan into the political, economic, and cultural space of Japan through “equal economic opportunity, legalization of mixed marriage, propagation of Japanese language, more emigration from Japan, and the publication of a newspaper by the Assimilation Society to promote friendship between the two peoples” (Chen 1972, 480, citing Itagaki Taisuke zenshū, pp. 395-412).

At the same time, Itagaki’s vision of assimilation imagined a boundary between Japan and Taiwan, and Taiwan and China, that Taiwanese Chinese elites would be able to transit. This double identity would be of significant value to the empire, and central to their role as Japanese subjects. As he talked about absorbing Taiwan into Japan, Itagaki portrayed Taiwan as a “path” between Japan and China. Taiwan would unite the two countries into a bulwark against Western imperialism in Asia.

“The purpose of our Assimilation Society is, in addition to achieving the goal of assimilation, to open a pathway (michi) for friendly relations with China. The enactment of this organization’s goals should not be the cause of any trouble for you Taiwanese islanders [Taiwanese Chinese] (Itagaki 1969, 400).

The pathway or bridge metaphor remained central to Taiwanese intellectual culture, albeit in many different forms (Heylen 2010, 161). The Assimilation Society, however, did not last long. The ethnic Han Chinese population of Taiwan supported the society, particularly the more elite families. In the society’s first month, 3,198 members signed up. Only 44 were Japanese. Yet the idea of assimilation unsettled the colonial government. The Government General of Taiwan watchfully tolerated Itagaki while he toured Taiwan. One month after his departure, however, the government’s tone abruptly changed. The island’s newspaper harshly criticized Japanese members of the society and the police revoked the society’s permit to meet. The society was effectively outlawed (Chen 1972, 480). Cai was fired from his job as a teacher at Tainan Number 2 Common School for participating in the society.