Fighting the Cabal from the Diet: Sanseitō and the Role of Conspiracy as Political Ideology

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October 10, 2025

Fighting the Cabal from the Diet: Sanseitō and the Role of Conspiracy as Political Ideology
Fighting the Cabal from the Diet: Sanseitō and the Role of Conspiracy as Political Ideology

Volume 23

Abstract: Sanseitō is a fringe Japanese political party founded during the coronavirus disease 2019 (COVID-19) pandemic that has won several seats in the National Diet since 2022. Initially coming to prominence as a promoter of anti-vaccine narratives, the party has since promoted a conspiracist worldview that connects to more conventional right-wing nationalism and addresses a much broader range of issues and beliefs. In this article we outline the core tenets of this worldview and examine how attention to its construction as a participative political ideology sheds light on the party’s political actions and motivations.

Keywords: Political parties, conspiracy worldview, conspiracy theories, party competition, Japan

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Volume 23

About the author:

Dr. Robert A. Fahey is an assistant professor of political science at the Waseda Institute for Advanced Study in Tokyo, Japan. His research interests include populism, polarisation, the effects of conspiracy theory belief, and Japanese politics. He is currently working on a series of large-scale surveys aimed at discovering what kinds of conspiracy beliefs are widespread in East Asian countries, and how those beliefs impact the political and social life of those nations.

Romeo Marcantuoni is a doctoral candidate at the Graduate School of Asia-Pacific Studies in Waseda University. His research is on contemporary Japanese opposition politics with a focus on the emotional dynamics of parties. He received his BA and MA from KU Leuven, Belgium.

The Asia-Pacific Journal: Japan Focus is a peer-reviewed publication, providing critical analysis of the forces shaping the Asia-Pacific and the world.

    About the author:

    Dr. Robert A. Fahey is an assistant professor of political science at the Waseda Institute for Advanced Study in Tokyo, Japan. His research interests include populism, polarisation, the effects of conspiracy theory belief, and Japanese politics. He is currently working on a series of large-scale surveys aimed at discovering what kinds of conspiracy beliefs are widespread in East Asian countries, and how those beliefs impact the political and social life of those nations.

    Romeo Marcantuoni is a doctoral candidate at the Graduate School of Asia-Pacific Studies in Waseda University. His research is on contemporary Japanese opposition politics with a focus on the emotional dynamics of parties. He received his BA and MA from KU Leuven, Belgium.