Possible future scenarios of both climate and socioeconomic changes are commonly used to assess the impacts and adaptation measures of climate change. This chapter provides an overview of the development of the common socioeconomic scenarios in Japan. The data prepared for the S-18 common socioeconomic scenario are population, number of households, and land use (building site areas by use). The actual impacts of climate change occur alongside social changes in the population, number of households, and land use, including vacant houses. These data are important in many fields, such as natural disasters, biodiversity conservation, and CO2 emission reduction, to formulate climate change impacts and adaptation strategies.