Koshigaya-shi

In the latest Population Census the population is about 341,000 (341,621 in 2020). Over the five years from 337,498 in 2015, it rose by about four thousand. At an already mature scale, it is a city growing gently.

What I want to note here is that, while the total population increases, the number of children faces slightly the other way. Those under 15 fell by a little under a thousand, from 44,429 (2015) to 43,497 (2020). In the same span the share aged 65 and over rose from 23.8% to 25.5%. Behind a rising total, the share of the elderly has already passed a quarter. The household-with-children share is 22.5% (2020), on the higher side among the three cities laid out this time. The land price of residential areas is about 150,000 yen per m². The Fiscal Capacity Index is 0.87 (2023), short of 1.0, in a structure where part of standard expenditure is made up by the national local allocation tax. The Childcare Waitlist moved at a low level, from 4 (2024) to 3 (2025), nearly flat. Why these numbers took this form cannot be read without going back over the history of a riverine lowland and a post town.

Koshigaya’s skeleton begins from the geography of low ground ringed by rivers. The Naka River flows along the eastern edge of the city, the Ayase River along the western edge, and the Motoara River through the center, a low-lying watery land where rivers and irrigation channels large and small thread the municipal area. This very geographic condition — blessed with water, and at the same time continually facing water — came to decide this town’s fate.

The first foundation is the highway and river transport of the Edo era. As a post town of the Nikko Kaido laid out in the Edo era, Koshigaya-juku was placed here. The records of 1843 count one honjin, four waki-honjin and fifty-two inns, with 1,005 houses within the post town, and it was tied to Edo by river transport as well. What economic geography would call “a post town opened at the node of highway and water transport” was this town’s first function. It was also the production center of the Koshigaya daruma (Bushu daruma), said to have begun in the Kyoho era of the Edo period, and several houses still carry on its making today.

The second foundation, which largely decided the town’s present form, is flood control. As urbanization advanced, the function by which the paddy fields had temporarily stored water — their retention capacity — declined, and preparing for flood damage became a challenge. So, from 1996, the Koshigaya Lake Town project began in the southeastern part of the city. Its core is the Osagami Regulating Reservoir — about 39.5 hectares in area, completed in 2014 — dug for flood control. In 2008 Koshigaya Lake Town Station opened, and on the shore of the regulating reservoir stood AEON Lake Town, one of the largest in the nation by site area. Then, in April 2015, Koshigaya moved to Core City status and opened a public health center. A post town opened in a watery lowland, a pond dug for flood control, and a new district born on the shore of that pond — this town’s form is the record of a history in which the ways of dealing with water piled in layers upon the geography of a low land ringed by rivers.

What characterizes Koshigaya-shi is that, while the total population rose by four thousand, the number of children fell by only a little under a thousand. The household-with-children share, at 22.5%, is on the higher side among the three cities laid out this time, and the absolute number of children too has not greatly collapsed. The new district laid out on the shore of the regulating reservoir gathering people, including young households, can be read behind this number. In the way children move, it stands in contrast with Tokorozawa, where children fell by sixty-four hundred over the same five years.

The Childcare Waitlist moved at a low level, from 4 to 3 — nearly flat. The fewness of waitlisted in a town where children are nearly held has a different meaning from a fewness that is the result of the absolute number of children thinning. It can be read as a fewness that is the result of having kept supply and demand roughly balanced while the number of children does not greatly collapse. Children nearly held, the share of the elderly past a quarter, and yet the total population still rising — in a Core City where these many flows advance, the waitlist figure too settles into a small range of swing. Even with the same “few waitlisted,” the way of reading changes entirely depending on whether children are increasing or decreasing behind it. Only by laying it beside Tokorozawa’s does that come into view.

Koshigaya, as a town opened in a watery lowland, holds several functions of its own. One is the area that keeps the history from the Edo era: the old built-up area of Koshigaya-juku, opened as a post town of the Nikko Kaido, and the production center of the Koshigaya daruma carried on since the Kyoho era. Another is the district of Koshigaya Lake Town laid out on the shore of the Osagami Regulating Reservoir, dug for flood control, holding AEON Lake Town — one of the largest in the nation by site area — and Koshigaya Lake Town Station. The Naka, Motoara and Ayase rivers still thread the municipal area today.

Koshigaya moved to Core City status in 2015, growing to a scale that holds its own public health center. From a watery post town, to a town that dug a pond for flood control, and further to a Core City holding a new district on the pond’s shore — the condition “low ground ringed by rivers” has swapped on different functions era by era. The post town’s river transport and the flood-control regulating reservoir are, at root, both set upon the same geography of a lowland blessed with water and facing water. The function of carrying water in the Edo era, of storing water in the Heisei era, and now of bustle on the shore of the stored water — each time the way of dealing with water changed era by era, Koshigaya has shown another face of the town.