On April 22, 2011, 1 month and 11 days after the Fukushima Daiichi Nuclear Power Plant (FNPP) accident, the ex-evacuation zone was set within a 20-km radius of the plant. The livestock abandoned and wild animals in and around the ex-evacuation zone have been extremely valuable for analyzing the environmental pollution and the biological effects of internal and external exposure to radiation. We have launched “A comprehensive dose evaluation project concernining animals affected by the FNPP accident (Affected Animal Project)” to establish an archive system composed of samples and data from animals around FNPP to deepen our understanding of the biological effects of radiation and to improve protection against radiation. The ultimate goal of this project is to contribute to integrated radiation protection for ecosystems and humans through studies of animals affected by the FNPP accident. In 2020, we published a book titled “Low-Dose Radiation Effects on Animals and Ecosystems” about the status of environmental contamination up to 7 years after the accident and the results obtained from the Affected Animal Project. This book is a sequel to that book and summarizes further findings 15 years after the accident.