2. Kesen RiverIwate Prefecture Kesennuma is a city in Miyagi Prefecture, Japan. As of 31 May 2017, the city had an estimated population of 65,367 and a population density of 197 inhabitants per square kilometre in 26,429 households. The total area of the city is 332.44 square kilometres . Large sections of the city were destroyed by the 2011 Tōhoku earthquake and tsunami and major fires on March 11, 2011. From Wikipedia, the free encyclopedia.