The purpose of this publication is to understand the development of the ASEAN?Japan relationship on the occasion of the 50th anniversary of ASEAN?Japan Friendship and Cooperation in 2023. This book provides an overview of Japan’s changing relationship with the ASEAN region and presents statistical analyses of trade, investment, and aid while considering the following two perspectives. The first perspective is that of the individual ASEAN countries regarding their relationship with Japan, taking into account diversity in stages of economic development and other factors. The second perspective is that of ASEAN as a whole regarding its relationship with Japan as an economic cooperation organization and the role of the ASEAN economy in a globalizing world economy.