The central puzzle in the study of Japanese foreign policy has been why Japan has continued to play a passive role in international affairs, despite its impressive economic and political power. Challenging this central puzzle, the core argument of this study is to present an alternative path for the study of Japanese foreign policy. In fact, in recent years Japanese foreign policy has become less dependent on the United States, more strategic towards Asia, and more energetic towards international and regional institutions. One of the main features is multilateralism in Japanese foreign policy, as shown by Japan's active participation in the regional institutions. In pursuing multilateralism, Japan cooperated closely with the only durable regional body in Southeast Asia, to wit, the Association of Southeast Asian Nations (ASEAN). Given the fact that East Asian regionalism has been driven by ASEAN, it is of utmost urgency to investigate the emerging partnership between Japan and ASEAN. My central thesis in this study is thus to put Japan's ASEAN policy into a proper perspective by asserting that Japan's new policy initiatives towards ASEAN are not reactive, nor are they exceptions in a broader framework of merely reactive foreign policy.

In writing this book, I have fortunately received enormous support and assistance from individuals and institutions. To begin with, I have received financial support from two institutions to carry out my book project. They are a three-year research subsidy by the Japanese government and Pache Research Subsidy of Nanzan University. Without these sources of financial assistance, it would not have been possible to undertake extensive field research in Japan and Southeast Asia. In undertaking my field research, I am especially indebted to the following institutions. In Bangkok, Chulalongkorn University's Institute of Asian Studies gave me a special opportunity to conduct my field research based in Bangkok. For this, I am grateful to Dr Khien Theeravit and Ms Saikew Thipakorn. In Singapore, I am indebted to the staff of the ASEAN Studies Centre for their time and assistance: Mr Rodolfo Severino, Dr Termsak Chalermpalanupap, and Ms Moe Thuzar. Also at the ASEAN Secretariat in Jakarta, I owe a great deal of thanks to the following staff who were kind enough to answer my questions: Alexander Lim, Bala Palaniappan, and Kris Sandhi Soekartawi.