In July 2025, Sanseitō (a.k.a. The Party of DIY !!) became the first far-right political party in postwar history to establish a stable presence in both Houses of the National Diet. With the party’s fringe nativist and ultraconservative positions having been considered taboo for so long, domestic as well as foreign media have reported the party’s success as if it were a catch-up moment for Japanese politics; the nation had, after all, seemed to fairly resistant to the global populist moment. But Sanseitō also augurs something that is relatively new: a model for a political party where conspiracy narratives touch every facet of its operation.
Founded in 2020, Sanseitō rose to initial prominence through its skepticism of the mRNA vaccines and pandemic measures—a position so central to its identity that it remains a political priority for the party. Indeed, at its heart, Sanseitō is a far-right conspiracy party. It has promoted unsubstantiated theories about the harmful effects of COVID-19 vaccines on its social media platforms, among a panoply of other theories and narratives. On the ground, the party organizes seminars, holds town halls, and supports protests by other conspiratorial groups. Since it entered the Diet, Saneitō has raised its fringe ideas to the level of parliamentary debate and participates in nonpartisan parliamentary groups that oppose vaccines and the World Health Organization.
Sanseitō also augurs something that is relatively new: a model for a political party where conspiracy narratives touch every facet of its operation.
Conspiracy theories are a tricky thing to define. Most definitions make little distinctions between justifiable theories and outlandish ones. Or, they are too strictly delineated, leaving little space for healthy forms of skepticism. Conspiracies, after all, can and do happen, and believing in one or two does not necessarily have any bearing on political behavior. They can, however, be used towards political ends, and this has become more noticeable in recent years with the UK’s Conservative Party and the Republican Party under U.S. president Donald Trump. Nevertheless, political parties rarely make conspiracy theorizing their entire political identity.
It is not hard to see why. Parties are essentially tools of the establishment, and the establishment relies heavily on the existence of a trusted public sphere. Within that, it may be possible to pick small fights with a limited set of targets, but it makes little strategic sense to systematically undermine the institutions you rely on for legitimacy and coverage. That makes Sanseitō an exceedingly rare case in that it is fully committed to conspiracy theorizing, even labeling itself as a force fighting against the massive conspiracy that is driving Japan—and the world—towards some nefarious end.
The far-right policies that made headlines for Sanseitō are primarily a reflection of a worldview in which “globalists” pursue their goal of spreading “globalism,” and are doing so under cover of obscurity. Take for instance how the party describes immigration policy and gender equality as part of a concerted globalist plan. In this view, both ideas threaten to undermine the integrity of the nation-state by imposing alien values that are purported to be incompatible with those on which Japanese society was built. In the Diet, lawmaker Yoshikawa Rina has called the popular push towards separate surnames for married couples as an idea that “originates from Marxism” and serves to “destroy a culture by targeting its family system.”
Marxism (likely in reference to “Cultural Marxism”) is invoked here as one method through which control is exerted by an otherwise non-ideological set of actors that include finance capital, pharmaceutical companies (“big pharma”), and wealthy philanthropists. Indeed, at the core of Sanseitō’s claims is the existence of a shadowy cabal, a set of vested interests that are said to be responsible for creating a structure in which Japan is uniquely victimized among the nations of the world, especially after the U.S. led occupation and its reforms, but also going back all the way to Japan’s experience with Christian missionaries. Sanseitō is able to make these connections between current-day COVID-19 vaccinations and seemingly unrelated historical events because they are backed by a concrete ideology. This is markedly different from the promotion of, or belief in, discrete theories. An ideology is far more holistic, and provides ways through which one can incorporate various forms of often conflicting information into a relatively stable narrative about the world.
This worldview is premised on an assumption that there exists, in some fashion, a massive web of conspiracies that needs to be uncovered and resisted. Political actors such as Sanseitō call on their supporters to theorize, speculate, and connect the dots. Indeed, scholars have found that conspiracy theorizing functions as its own form of rationality and empiricism complete with “elite” opinion-makers in the form of charismatic figures (such as the enigmatic “Q”) and algorithmically-charged social media influencers.
What stands out in this case is that Sanseitō has incorporated the logic of conspiracy into the party itself, shaping the way it organizes and mobilizes its resources. This provides Sanseitō with a number of advantages that other emerging parties struggle to attain such as reliable access to media, funding, and manpower. Content platforms such as YouTube, X, and TikTok facilitate this, and Sanseitō uses their affordances to great effect. Loosely moderated and easily monetized, social media platforms provide anti-establishment parties with the means to build a strong competitive advantage as well as proactively erode public trust. Part of Sanseitō’s value proposition, after all, is access to fringe interpretations of current events through its members-only content, mailing lists, and in-person events. This not only lets them speak directly to their supporters, it also incentivizes legacy media to respond to diversifying demands by reflecting fringe political priorities.
Another one of its innovations is in its party membership system. Membership is organized in tiers, with each giving more access to content and pathways to action—arguably analogous to the marketing concept of a “payment funnel.” Each step produces more buy-in, gradually socializing members while allowing the party to set a higher ceiling on dues than other parties. Anecdotal data and reporting has also suggested that Sanseitō members are well-organized, dedicated, and effective. Together with the party’s proven ability to recruit broadly and still maintain much of its message discipline suggests a capacity to attract, retain, and train its members that is rare for a party of its still modest size.
All of this is to say that, with its conspiracy ideology, Sanseitō has tapped into something that goes far beyond the mobilization of the latent far-right, and it is the normalization of this nascent worldview that should worry us more than the party’s numerical growth. After all, every official victory that Sanseitō achieves will increase the legitimacy of its interpretations of political reality. And so, if the values of liberal democracy are to be defended, Japan (like much of the world) will have to devise a response to limit these gains. This may be difficult, as Sanseitō’s views are not as much of a political taboo as they once were. Major political parties, both in government and in opposition, have little to no qualms cooperating with Sanseitō on legislation. Even the election of Takaichi Sanae to president of the LDP (and thereby prime minister of Japan) was at least in part influenced by Sanseitō’s recent growth.
The far-right frame remains entirely applicable (Sanseitō’s beliefs have long been present in the ideological infrastructure of the far-right), but it is this conspiracy worldview that has allowed it to knit together a far-right base of support with voters more generally distrustful of government or resentful of the establishment. Failure to recognize this puts us at risk of losing track of the battle lines currently being drawn in Japan’s changing political landscape.
Romeo Marcantuoni is a PhD candidate at the Graduate School of Asia-Pacific Studies at Waseda University and Adjunct Lecturer of Political Science at Temple University Japan Campus. He earned his MA and BA in Japanese Studies at KU Leuven, Belgium. His current research focuses on interpretive approaches to the study of political parties from the perspective of emotions and narrative.
