This town’s coast is deeply intricate. A coastline where the mountains press to the sea and inlets are cut into each valley continues long. In one of those inlets, at the mouth where a large river empties into the sea, a castle town opened. Blessed with the bounty of mountain and sea, this castle town was, of old, said to be a place where "the lord is sustained by the inlets, and the inlets are sustained by the mountain’s bounty." This castle town holding an intricate sea and river bound eight surrounding towns and villages into one, becoming the widest city in the prefecture and one of the widest in Kyushu, and now has quietly lost population. Saiki’s numbers are the record of a town in which the ria coast and the wide city area are inscribed.
A city that opens at the southern tip of Oita Prefecture, touching Miyazaki Prefecture. Because in 2005 the castle town city merged with eight surrounding towns and villages, the step in the population for the city area appears largely between 2000 and 2005, when the merger is reflected in the Census. Seen as the castle town city alone, the population was 50,120 in 2000; for the city area after the merger it was 80,297 in 2005, and from there it has fallen to the 66,851 of 2020. What I (Atlas) want to read here is not the sign "a city of the south of the prefecture," but the causal thread: how the past of the ria coast and the wide city area is translated into today’s population and finances.
01 · Seeing the present Saiki in its numbers
In the latest Population Census the population is about 67,000 (66,851 in 2020). Because in 2005 the castle town city merged with eight surrounding towns and villages, the step in the population for the city area appears largely between 2000 and 2005, when the merger is reflected in the Census. Seen as the castle town city alone, the population was 50,120 in 2000; for the city area after the merger it was 80,297 in 2005, 76,951 in 2010, and 66,851 in 2020 — falling.
Looking inside, the figure of a wide city holding an intricate sea and mountains appears. The share aged 65 and over rose from 36.8% in 2015 to 40.9% in 2020, passing four in ten. The household-with-children share is 16.6% in 2020, the crude birth rate is 5.5 per thousand in 2020, and the Childcare Waitlist was zero in both 2024 and 2025. The Fiscal Capacity Index was 0.33 in fiscal 2023 — a level able to cover only a little over three-tenths of expenditure with its own tax revenue, with a large degree of reliance on the local allocation tax. The figure of a castle town holding an intricate sea and river, losing population after gaining a wide city area through the merger, shows in the numbers. Why it takes this form cannot be read without going back to the past of the ria coast, the castle town and the merger.
Source: Population Census (Statistics Bureau, MIC) / Local Government Finance Survey, Fiscal Capacity Index (MIC) / Childcare Facility Status Report (Children and Families Agency) / Real Estate Information Library (MLIT)
02 · The ria coast, the mouth of the Bansho River, the castle town of the Mori family, the merger of eight towns and villages — the history behind the numbers
This town’s skeleton is set by the landform of an intricate coast where the mountains press to the sea, the mouth of a large river, the domain’s castle town, and the merger of eight towns and villages. The starting layer is the intricate coast and the river. This land holds a deeply intricate coast, where the mountains press to the sea and inlets are cut into each valley. In one of those inlets, at the mouth where a large river flowing down from the mountains empties into the sea, a flatland opened. The intricate sea brought fish, the river and the flatland brought fields, and the mountains behind brought timber. The intricate coast and the river mouth into which it empties were the foundation of this town.
Upon this river-mouth land, the domain’s castle town stood. On the flatland of this river mouth opened the castle town of a domain governed by one family, so blessed with the bounty of sea and mountain that it was said "the lord is sustained by the inlets, and the inlets are sustained by the mountain’s bounty." The path to becoming a city, too, mirrors this town. In 2005 the castle town city merged with eight surrounding towns and villages, becoming the widest city in the prefecture and one of the widest in Kyushu. The ria coast, the mouth of the Bansho River, the castle town of the Mori family, and the merger of eight towns and villages — this town’s form stands upon the past of the intricate coast and the castle town that the land where the mountains press to the sea carved.
Source: Saiki City / Saiki Castle and the Mori family (opening at the mouth of the Bansho River, the castle town of the Mori family of the Saiki domain, of which it was said "the lord of Saiki is sustained by the inlets," a land of the bounty of sea and mountain — overview) / Saiki City / the ria coast (holding an intricate ria coast and blessed with the bounty of the sea; at the southern tip of Oita Prefecture, touching Miyazaki Prefecture — overview) / Saiki City (established on 2005-3-3 by the new merger of the former Saiki City and five towns and three villages of Minamiamabe County; the city area is the largest in Oita Prefecture and one of the widest in Kyushu — overview)
03 · In a castle town holding an intricate sea and river, losing population after the merger
What characterizes Saiki is that, while it holds the past of a castle town holding an intricate sea and river, it is losing population after gaining a wide city area through the merger. The 50,120 of 2000, seen as the castle town city alone, became 80,297 in 2005 as the city area greatly widened through the merger, but from there it has fallen to the 66,851 of 2020. Even in this castle town blessed with the bounty of sea and mountain, in the fishing villages scattered through each inlet of the intricate coast and the settlements of the mountains behind, one can read that some of the younger generation moved toward the larger cities, and the town’s age as a whole rose. That the share aged 65 and over passed four in ten at 40.9% in 2020 is an expression of that.
On the other hand, the Childcare Waitlist was zero in both 2024 and 2025, the household-with-children share is 16.6% in 2020, and the crude birth rate is 5.5 per thousand in 2020. The Fiscal Capacity Index of 0.33 is a level able to cover only a little over three-tenths of expenditure with its own tax revenue, showing the large degree of reliance on the local allocation tax seen in common across lands where settlements are scattered through a wide city area. The castle town holding an intricate sea and river now, after gaining a wide city area through the merger, advances its aging while losing population. Because settlements are scattered through a wide city area, each fall works on the city as a whole; because the younger generation moves to the larger cities, the age rises; because the tax source is thin, it relies on the allocation tax — these three branch from the same landform of the mountains pressing to the sea.
Source: Population Census (Statistics Bureau, MIC) / Local Government Finance Survey, Fiscal Capacity Index (MIC) / Childcare Facility Status Report (Children and Families Agency)
04 · A land where the mountains press to the sea held a castle town and a wide city area, this past
The functions Saiki holds are not one. It holds a deeply intricate coast where the mountains press to the sea and inlets are cut into each valley, with fishing villages scattered through each of those inlets. At the mouth where a large river flowing down from the mountains empties into the sea, the domain’s castle town, blessed with the bounty of sea and mountain, opened, of which it was said the lord is sustained by the inlets. And the castle town city bound eight surrounding towns and villages, becoming the widest city in the prefecture and one of the widest in Kyushu.
From the ria coast, to the mouth of the Bansho River, the castle town of the Mori family, and the merger of eight towns and villages — the geography of "a land where the mountains press to the sea and inlets are cut into each valley" gave rise to the intricate coast and opened a castle town at the river mouth. Upon the position of the southern tip of Oita Prefecture, the intricate coast and the castle town of the river mouth are folded together, and set the present form of Saiki.
Source: Saiki City / Saiki Castle and the Mori family (opening at the mouth of the Bansho River, the castle town of the Mori family of the Saiki domain, of which it was said "the lord of Saiki is sustained by the inlets," a land of the bounty of sea and mountain — overview) / Saiki City / the ria coast (holding an intricate ria coast and blessed with the bounty of the sea; at the southern tip of Oita Prefecture, touching Miyazaki Prefecture — overview) / Saiki City (established on 2005-3-3 by the new merger of the former Saiki City and five towns and three villages of Minamiamabe County; the city area is the largest in Oita Prefecture and one of the widest in Kyushu — overview)
05 · Atlas’s note — in a castle town holding an intricate sea and river, reading the bounty of the landform and the scattering
Lay out Saiki’s numbers and the indicators of a wide city holding an intricate sea and mountains line up: a population falling after the city area widened through the merger, an aging rate of 40.9%, a household-with-children share of 16.6%, and a fiscal capacity of 0.33. What I want to read here is that this town "gained, through the 2005 merger, the widest city area in the prefecture and one of the widest in Kyushu." Seen as the castle town city alone the population was around fifty thousand, but through the merger the city area greatly widened and it passed eighty thousand. But through that wide city area, fishing villages of each inlet of the intricate coast and settlements of the mountains behind are scattered, and if population falls in each one of them, the population of the whole wide city area greatly falls. The composition by which, unless one reads the wide city area and the scattering of people separately, one mistakes the image, explains this town’s numbers well.
Another thing I want to consider is the overlap of the bounty of sea and mountain in this town, of which it was said "the lord is sustained by the inlets, and the inlets are sustained by the mountain." The landform of the mountains pressing to the sea has brought both the fish of the intricate sea and the timber of the mountains behind to the same single castle town. But that same landform scatters settlements inlet by inlet, valley by valley, and now appears in the form of a fall of population and an aging passing four in ten. The bounty of sea and mountain the landform brought, and the harshness of the scattering that landform brings, overlap in the same single city.
Stand at the mouth of the Bansho River at dusk, and the lights of fishing villages flicker scattered through each valley’s inlet. Whether living continues in each one of them is the very substance of the number of an aging that has passed four in ten. What I (Atlas), who handle numbers with the eye of accounting, can say is to note down here the castle town that held the bounty of sea and mountain, and the settlements scattered through the inlets.
Source: Population Census (Statistics Bureau, MIC) / Saiki City / Saiki Castle and the Mori family (opening at the mouth of the Bansho River, the castle town of the Mori family of the Saiki domain, of which it was said "the lord of Saiki is sustained by the inlets," a land of the bounty of sea and mountain — overview) / Saiki City / the ria coast (holding an intricate ria coast and blessed with the bounty of the sea; at the southern tip of Oita Prefecture, touching Miyazaki Prefecture — overview) / Saiki City (established on 2005-3-3 by the new merger of the former Saiki City and five towns and three villages of Minamiamabe County; the city area is the largest in Oita Prefecture and one of the widest in Kyushu — overview)
Editor’s note: all figures and sources are drawn from official statistics. The prose follows Atlas’s voice, and AI (atlas-handcrafted-reverse-v1 (wave32-west 2026-06-04)) handled the shaping of the text. Evaluative or predictive language (such as “a good buy” or “attractive”) is intentionally left out. Revision id: wave32w_