This chapter aims to study the phenomenon of authoritarization of contemporary Japanese politics under Shinzo Abe’s administration from 2012 to date, from a constitutionalist point of view. We think it is worth analysing the case of Japan because it allows us to consider whether Japan can be counted as a country which shows a movement towards becoming a ‘competitive authoritarian regime’ (David Landau), having been a liberal democracy. For this reason, the research interest is to identify how this authoritarization of Japanese constitutionalism has developed, and to what extent, under the current Abe administration. Enjoying a vast majority of seats in both Houses of the Parliament under a parliamentary cabinet system in the Westminster model, the coalition of his Liberal Democratic Party and Komeito, a right of centre Buddhist party has succeeded in trying to change the functions of the current governmental systems in a manner that largely makes them more authoritarian than was previously the case. Most interestingly, the Japanese political and legal systems operate within the bounds of their own constitutional frameworks despite public opinion being harshly critical of them. A good example is the very controversial military legislation adopted in September 2015 concerning activities of the Self-Defense Forces. Furthermore, it is important to examine a constitutional amendment draft published in 2012 and Abe’s personal concrete idea of constitutional amendment from the perspective of authoritarization of constitutionalism.