The March 2011 disasters exposed the ineffectiveness of Japan’s political leaders, evoking three broad questions. First, why did the Kan cabinet fail to provide effective leadership in response to the disasters and why was a succession of governments unable to guide Japan out of the seemingly interminable economic malaise of the “lost decades”? The fact that Japan’s leaders possess similar powers to those of counterparts in other democratic polities suggests that a dysfunctional cabinet system is the culprit. So why is it that Japan has parliamentary democracy in form but not in practice? This is puzzling given that postwar Japan has been governed under institutional arrangements modeled after Britain’s “Westminster system,” and yet cabinet government has not set root. And, third, what gives Japan’s parliamentary cabinet system its characteristic form and function? This draws attention to the shaping effect and distributional consequences of institutions, as well as the role of critical junctures in creating strategic openings for change. And so, to understand Japan’s cabinet system, it is essential to trace its evolution. This leads backward in time from the recent challenges of “Twisted Diets” and coalition governments to institutional solutions rendered by reformers in the 1990s, the legacies of protracted single-party rule, actions taken by American occupation planners, prewar technocrats, and party leaders, and, ultimately, to a cabal that emerged in the aftermath of the Meiji Restoration. The development of the cabinet system can be seen as a proxy for Japan’s experiment with democratic governance in the longue durée.