This island floats just between mainland Kyushu and the peninsula of the neighboring country across the sea. On this island on the border between states, through the Edo age a single family exclusively bore the diplomacy and trade with the neighboring country, and continued for fifteen generations. The family placed a house at a port across the sea, handed over silver and copper, and received ginseng and silk. This island on the border between states was established as a city by binding six towns anew into one, and has now quietly lost population. Tsushima’s numbers are the record of a town in which a family that monopolized diplomacy and Fuchu are inscribed.
A city of a border island of Nagasaki Prefecture, floating between mainland Kyushu and the peninsula of the neighboring country across the sea. Because this city was established in 2004 by binding six towns on the island anew into one, the statistics cover the period from 2005, after the city’s establishment, on. The population has fallen from the 38,481 of 2005 to the 28,502 of 2020. What I (Atlas) want to read here is not the sign "an island city of the prefecture’s north," but the causal thread: how the past of a family that monopolized diplomacy and Fuchu is translated into today’s population and finances.
01 · Seeing the present Tsushima in its numbers
In the latest Population Census the population is about 29,000 (28,502 in 2020). Because this city was established in 2004 by binding six towns on the island anew into one, its population statistics as a city cover the period from 2005, after the establishment, on. From the 38,481 of 2005, through the 34,407 of 2010, the 31,457 of 2015, to the 28,502 of 2020, it has fallen.
Looking inside, the figure of a city of an island on the border between states appears. The share aged 65 and over rose from 33.9% in 2015 to 38.6% in 2020, nearing four in ten. The household-with-children share is 16.4% in 2020, and the Childcare Waitlist was zero in both 2024 and 2025. The Fiscal Capacity Index was 0.20 in fiscal 2023 — a level able to cover only about two-tenths of expenditure with its own tax revenue, with a large degree of reliance on the local allocation tax. Fuchu, where a family monopolized the diplomacy with the neighboring country, now loses population and advances its aging after the merger. Why it takes this form cannot be read without going back to the past of the border, the diplomacy 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 island on the border between states, the family that monopolized diplomacy, the house at Busan, a merger of six towns — the history behind the numbers
What supports Tsushima’s past is the island’s position on the border between states, the family that monopolized diplomacy at that border, the house it placed at a port across the sea, and the merger of six towns. The oldest layer is the border and the family. This island floats just between mainland Kyushu and the peninsula of the neighboring country across the sea. On this border island, through the Edo age a single family exclusively bore the practical diplomatic affairs and trade with the neighboring country — the only one the Tokugawa shogunate had formal relations with — and continued for fifteen generations. The town called Fuchu was that family’s castle town. The border and the family that monopolized diplomacy are this island’s oldest foundation.
This family placed a house across the sea. At a port of the neighboring country, a house that became a base of diplomacy and trade was placed; from Japan, silver and copper, and from the neighboring country, ginseng, raw silk and silk textiles were traded. It was a diplomatic and trading role peculiar to an island on the border between states. The newest layer is the path to becoming a city. In 2004 the six towns on the island were bound anew into one, and the present city was established. The border island, the family that monopolized diplomacy, the house at Busan, the merger of six towns — the land that piled these four layers in order of age is the present Tsushima.
Source: Tsushima City / the So family (a border island between mainland Kyushu and the Korean peninsula; through the Edo period the So family exclusively conducted the diplomatic affairs and trade with Korea — the only state Japan had formal relations with under the Tokugawa shogunate — for fifteen generations; Izuhara [the former Fuchu] was the castle town — overview) / Tsushima City / the Japan House at Busan (the Tsushima domain placed a Japan House at Busan in Korea as a base for Japan–Korea diplomacy and trade; the 1609 Kiyu Treaty laid down the basis of Japan–Korea trade, by which Japan supplied silver and copper, and Korea ginseng, raw silk and silk textiles — overview) / Tsushima City (city status enacted on 2004-3-1 by the new merger of Izuhara, Mitsushima, Toyotama, Mine, Kamiagata and Kamitsushima Towns on Tsushima Island; population at establishment about 41,000 — overview)
03 · On an island on the border between states, losing population and advancing aging after the merger
What characterizes Tsushima is that, while it holds the past of Fuchu, where a family monopolized diplomacy, it is losing population and advancing its aging after the merger. From the 38,481 of 2005, when the city was established, to the 28,502 of 2020, some ten thousand were lost over fifteen years. Even on this island that once bore diplomacy and trade on the border between states, from modern times on it became an island land centered on fishery, and one can read that some of the younger generation moved toward the larger cities and the Kyushu mainland and the town’s age as a whole rose. That the share aged 65 and over neared four in ten at 38.6% in 2020 is an expression of that.
On the other hand, the Childcare Waitlist was zero in both 2024 and 2025, and the household-with-children share is 16.4% in 2020. The Fiscal Capacity Index of 0.20 is a level able to cover only about two-tenths of expenditure with its own tax revenue, showing the large degree of reliance on the local allocation tax seen in common across island lands cut off from the mainland by sea. The population fell after the merger, the aging neared four in ten, and the body of the finances is not thick on tax revenue alone. What overlap of numbers Fuchu, which bore diplomacy, has now reached — that comes into view only when population, age and finances are laid out on a single sheet.
Source: Population Census (Statistics Bureau, MIC) / Local Government Finance Survey, Fiscal Capacity Index (MIC) / Childcare Facility Status Report (Children and Families Agency)
04 · An island on the border between states held Fuchu, the castle town of a family that monopolized diplomacy
The functions Tsushima holds are not one. It has the face of an island on the border between states, floating just between mainland Kyushu and the peninsula of the neighboring country across the sea. It also has the face of Fuchu, the castle town of a family that monopolized diplomacy, where at that border a single family exclusively bore the diplomacy and trade with the neighboring country through the Edo age and placed a house at a port across the sea. The landform and position of floating between the mainland and the peninsula of the neighboring country gave this island both the role of a border and the function of diplomacy and trade.
An island on the border between states held Fuchu, the castle town of a family that monopolized diplomacy — that is the town Tsushima is. From the border between states, to the family that monopolized diplomacy, the house at Busan, and the merger of six towns, what set the skeleton was the geography of "an island floating between mainland Kyushu and the peninsula of the neighboring country." Precisely because it floated on the border, a role belonging neither to the mainland nor to the neighboring country came round to this island. It is a rare island where position itself became the calling of diplomacy.
Source: Tsushima City / the So family (a border island between mainland Kyushu and the Korean peninsula; through the Edo period the So family exclusively conducted the diplomatic affairs and trade with Korea — the only state Japan had formal relations with under the Tokugawa shogunate — for fifteen generations; Izuhara [the former Fuchu] was the castle town — overview) / Tsushima City / the Japan House at Busan (the Tsushima domain placed a Japan House at Busan in Korea as a base for Japan–Korea diplomacy and trade; the 1609 Kiyu Treaty laid down the basis of Japan–Korea trade, by which Japan supplied silver and copper, and Korea ginseng, raw silk and silk textiles — overview) / Tsushima City (city status enacted on 2004-3-1 by the new merger of Izuhara, Mitsushima, Toyotama, Mine, Kamiagata and Kamitsushima Towns on Tsushima Island; population at establishment about 41,000 — overview)
05 · Atlas’s note — on an island on the border between states, reading the past in which position became the calling of diplomacy
Lay out Tsushima’s numbers and the indicators of a city of an island on the border between states line up: a population falling after the merger, an aging rate of 38.6%, a household-with-children share of 16.4%, and a fiscal capacity of 0.20. But when I (Atlas), as a certified public accountant, read these, what I want to read here is the singularity of this island’s position — that it "floats just between mainland Kyushu and the peninsula of the neighboring country across the sea." Because of that border position, a single family exclusively bore the diplomacy and trade with the neighboring country through the Edo age and placed a house at a port across the sea. The chain by which the role given precisely because it is a border island, belonging neither to the mainland nor to the neighboring country, set this island’s history explains this town’s map well.
Another thing I want to consider is the thinness of the tax revenue — a Fiscal Capacity Index of 0.20. Because it is an island cut off from the mainland by sea, industry is hard to draw in and the tax source is not thick. Even the island that was once Fuchu, the castle town of a family that monopolized diplomacy on the border between states, has, from modern times on, yielded that role to the state and, as an island land centered on fishery, lost population and advanced its aging to near four in ten.
The position of floating on a border belonging neither to the mainland nor to the neighboring country once gave the island the calling of monopolizing diplomacy, and now leaves the island the thin tax source of an island where industry is hard to draw in. Whether to view this island as the land of Fuchu where a family bore diplomacy, or as a fishing city cut off by sea, will divide how Tsushima appears. The position of floating on a border belonging neither to the mainland nor to the neighboring country once gave the island the calling of diplomacy, and now leaves the island a thin tax source.
Source: Population Census (Statistics Bureau, MIC) / Tsushima City / the So family (a border island between mainland Kyushu and the Korean peninsula; through the Edo period the So family exclusively conducted the diplomatic affairs and trade with Korea — the only state Japan had formal relations with under the Tokugawa shogunate — for fifteen generations; Izuhara [the former Fuchu] was the castle town — overview) / Tsushima City / the Japan House at Busan (the Tsushima domain placed a Japan House at Busan in Korea as a base for Japan–Korea diplomacy and trade; the 1609 Kiyu Treaty laid down the basis of Japan–Korea trade, by which Japan supplied silver and copper, and Korea ginseng, raw silk and silk textiles — overview) / Tsushima City (city status enacted on 2004-3-1 by the new merger of Izuhara, Mitsushima, Toyotama, Mine, Kamiagata and Kamitsushima Towns on Tsushima Island; population at establishment about 41,000 — 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 (wave30-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: wave30w_