Book excerpt: The contributors to this book demonstrate empirically how Japanese public opinion is formed amid strained Japan–South Korea relations. Studying public opinion in Japan and South Korea is critically important for exploring the causes and consequences of the deterioration of the relationship between the two countries. Japan–South Korea relations are at their worst level since World War II. Faced with North Korea’s nuclear threat and China’s regional and global advances, Japan and South Korea are each allied with the US and function as key stabilizers within the Asia–Pacific "Pax Americana." These relations play a decisive role in East Asia’s international security. The contributors explore a variety of social scientific methodologies—both conventional quantitative surveys and experiments, as well as quantitative text analyses of published books and computational analyses of social media data—to disentangle the dynamic relationship between Japanese public opinion and Japan–South Korea relations. An invaluable resource for scholars of East Asian regional security issues.