After a brief look at the current situation in Fukushima, this introduction presents the central focus of the book: identifying new legacies of post-Fukushima activism. Civil Society Organisations (CSOs) carried out more than ten years of activities to improve government policies on radiation and to support evacuees from affected areas. This introduction argues that the key points and potential pitfalls in CSOs’ advocacy and longevity, revealed through these long-term activities, constitute these legacies. The introduction also provides an overview of the analytical frameworks, data, and methodologies employed, and outlines the structure of the book.