The Trans-Pacific Partnership (TPP), which has been led by Japan and the United States, lost the momentum as President Trump officially withdrew the United States from the Trans-Pacific Partnership, and ‘TPP without US’ raised doubts on its effect and sustainability. But, Japanese Prime Minister Shinzo Abe declared that ‘TPP 11 without US’ will be continued; As of January 2018, the pact continues in the form of Comprehensive and Progressive Trans-Pacific Partnership(CPTPP), under Japan’s proactive and enthusiastic role. What are the reasons for Japan to promote TPP, a symbol of US-Japan cooperation in such proactive and enthusiastic manner even without the United States? More fundamentally what motivates Japan to promote economic cooperation with the US instead of China, major trading partner within the region? To answer these questions, this research aims to understand the changes of Japan’s national identity, regional recognition, and regional initiative in the historical context of international politics, and further, investigate the domestic and international economic benefits and security interests that could result from participation and continuation of TPP from Japan’s standpoint.