Tachikawa is a city located in the western portion of the Tokyo Metropolis, Japan. As of 1 March 2021, the city had an estimated population of 1…Tachikawa is a city located in the western portion of the Tokyo Metropolis, Japan. As of 1 March 2021, the city had an estimated population of 184,383 in 93,428 households, and a population density of 7,600 persons per km². The total area of the city is 24.36 square kilometres.