This book moves away from the common belief that Japan’s international relations are firmly the preserve of the national government in Japan’s highly centralised political system. Examining examples of subnational governments (SNGs) across Japan the book uncovers a significant and generally unrecognised development in Japanese politics: SNGs are ever more dynamic international actors as national borders ‘weaken’ across the world. Exploring what Japanese SNGs do, where they do it, and why, the book considers the implications of these factors for Japan’s international relations and domestic politics. By bringing to light the scope and consequences of the international actions of Japan’s SNGs, this book provides a more accurate and nuanced understanding of the country’s foreign policy, at a time when it is pursuing a broader and more active profile in international affairs.