ABSTRACT For almost 80 years, post-war Japanese moral education has adopted a dual-process structure, which states morality is taught through two processes: one through all aspects of school education and the other through a special moral education class. The necessity and effectiveness of this structure were theorised by Eijiro Inatomi. However, it has been almost neglected that his theory is largely based on Aristotle’s theory of virtue. This paper examines Inatomi’s Aristotle-inspired theory and its significance. After reviewing the social and historical background of his theory, I argue that Inatomi successfully adopted Aristotle’s theory of virtue in three respects: human definition, intellectual virtue, and ethical virtue. Finally, I suggest that post-war Japanese moral education can be understood as a nationwide social implementation experiment on the efficacy of Aristotelian virtue ethics and that Inatomi’s notion of cosmos can serve as a conceptual device to enhance the social feasibility of Aristotle’s virtue ethics.