This introduction presents an overview of the key concepts discussed in the subsequent chapters of this book. The book explores the development of Japan's strategic partnerships in the Asia-Pacific and beyond. It reviews Japan's links with China, the main driver behind Japan's quest for regional partnerships. The book examines Japan's evolving relations with the United States, the country's main security provider but also a factor of uncertainty for the long-term sustainability of the alliance. It explores drivers, outcomes and obstacles in Japan's partnership efforts with India, Australia, the Association of Southeast Asian Nations (ASEAN), South Korea, and Europe. The book argues that Japan, especially since the beginning of the 2010s, has significantly stepped-up its economic and public diplomacy efforts vis-a-vis ASEAN. It looks at the impact of transatlantic relations during the Trump presidency. The book assesses the extent to which Japan can develop a strategic security partnership with Europe.