Because Kaisei is an alluvial fan on the Sakawa River basin, it is a flatland with a gentle lean to the south. Although it is the smallest town in Kanagawa Prefecture, as it is 1.7km long from east to west and 3.8km long from north to south for a total area of 6.55k㎡, it has fertile ground, good water irrigation, a warm climate, and good transportation methods. It is a modern rustic town that is easy to live in because it is very convenient and close to the water.