Sea level rise poses significant inundation risks to coastal areas worldwide. Chap. 11 evaluates the impacts of inundation, the effectiveness of adaptation measures, and the associated costs in Japanese coastal areas. First, we estimate the potentially inundated areas, affected populations, and economic damages under two greenhouse gas emission scenarios: RCP8.5-SSP5 (high emissions) and RCP2.6-SSP1 (low emissions). We then examine two primary adaptation measures—protection and relocation—by estimating their effectiveness and costs, and we identify the most suitable approaches for climate change adaptation in Japanese coastal regions. The results show that RCP2.6-SSP1 resulted in smaller inundated areas, fewer affected populations, and lower economic damages compared to RCP8.5-SSP5, highlighting the importance of mitigation efforts. Additionally, the findings indicate that relocation costs are higher overall than protection costs in Japan. However, the cost relationship between these two strategies varies depending on population distribution and socioeconomic conditions across different regions.