This paper adopts a unified approach to an understanding of the development processes of the East Asian economies, Chinese, Japanese and South Korean, in terms of common five phases starting with Malthusian equilibria and extended to forthcoming post-demographic transitions characterized by the shrinkage of the working-age group share in the population. Notwithstanding of the basic commonality, however, there are also marked differences among the East Asian economies in the timing of turning points, durations, and substantive forms of the phases. The paper claims that those differences need to be co-explained by accompanying variations in institutional trajectories. It identifies the Malthusian origins of contrasting political-economic and social-norm characteristics in Chinese and Japanese institutional arrangements and discusses their transformations over successive phases. By delineating institutional characteristics of China and Japan from a game-theoretic perspective, it implicitly challenges prevailing views that contrast the East and the West in such general terms as kinship vs. the third party enforcement of contracts, Confucianism vs. Protestantism, collectivism vs. individualism, authoritarianism vs. liberal democracy, and the like. These dichotomies are too simplistic for explaining the uniqueness, commonality and variations of institutional arrangements in East Asia and their impacts on development processes of respective economies.