Japan’s Remote-Island (Ritō) Policy: Security and Resilience Lessons for Island Governments

The short version

This explainer answers a practical question for island and coastal governments: what does Japan’s published ritō framework actually say about security, disaster isolation and lifeline dependence, and which parts travel? It sits in ISPI’s governance and Pacific security hub and emergency preparedness hub, with a maritime-supply read-through to the supply chain and infrastructure hub and the ports and maritime security research hub. It extends the editorial-log item on Japan’s archipelago resilience (W24) as East Asia piece E1.

Japan is an archipelagic state with a continental hinterland, but that does not cancel island geometry. Designated remote islands under the main Act exclude Okinawa, Amami and Ogasawara, which have separate special-measures statutes; even so, national law treats ferry fares, port calm-water works, tsunami isolation and depopulation as one policy problem (MLIT Remote Islands Development page; MLIT, Measures Taken for Remote Island Development in FY2024 (subcommittee report, Dec. 5, 2025)).

What does Japanese law mean by ritō?

The Remote Islands Development Act (離島振興法, Act No. 72 of Shōwa 28 / 1953) states its purpose in Article 1: remote islands play important roles in conserving Japan’s territory and exclusive economic zone, using marine resources, transmitting culture, conserving the natural environment, introducing renewable energy, providing nature contact and securing food supply—yet they face severe natural and social conditions, including long-running population decline and rapid aging, and higher costs for travel and essential goods (Remote Islands Development Act (e-Gov)).

Article 1-2 requires measures that improve those conditions, promote exchange, prevent uninhabited islands and sharp population loss, and promote settlement (Remote Islands Development Act (e-Gov)). Competent ministers designate development areas (Article 2) and issue a national Basic Policy (Article 3); prefectures prepare plans covering routes, air links, ports (including bridges), airports, roads, freight-cost reduction, industry, medical care, energy and disaster prevention including earthquake and tsunami damage (Remote Islands Development Act (e-Gov); MLIT, Remote Islands Development Basic Policy page).

A 2022 amendment (Act No. 92 of Reiwa 4), effective April 1, 2023, extended the Act by ten years and added “related population,” a prefectural support duty toward remote-island municipalities, richer plan contents and stronger consideration clauses (MLIT, Measures Taken for Remote Island Development in FY2024 (subcommittee report, Dec. 5, 2025)). The Act loses effect on March 31, Reiwa 15 (2033) (Remote Islands Development Act (e-Gov)). The Basic Policy was gazetted March 31, 2023 (MLIT, Remote Islands Development Basic Policy page; MLIT, Basic Policy for Remote Island Development Areas (PDF)).

How large is the designated remote-island estate?

MLIT’s FY2024 measures report to the National Land Council’s Remote Island Development Subcommittee states that, as of April 1, 2025 (Reiwa 7), 77 regions were designated under the Act, comprising 256 islands, about 5,316 square kilometers and a population of about 340,000 (MLIT, Measures Taken for Remote Island Development in FY2024 (subcommittee report, Dec. 5, 2025)). The same report’s Reference I-2 table lists 111 related municipalities; population is taken from the 2020 census (Oct. 1, 2020), and area from the Japan Remote Island Center’s Remote Island Statistical Yearbook 2023 (MLIT, Measures Taken for Remote Island Development in FY2024 (subcommittee report, Dec. 5, 2025)).

MLIT’s public Remote Islands Development landing page, checked on Nov. 7, 2026, states that excluding Okinawa, Amami, Ogasawara and similar areas, 77 regions and 255 islands are designated as of April 1, 2026 (Reiwa 8) (MLIT Remote Islands Development page). The one-island difference between the April 2025 report and the April 2026 page is a designation change, not an ISPI estimate. Either way, the order of magnitude is stable: a few hundred inhabited remote islands and roughly a third of a million residents under the main Act.

The same report’s island-composition table shows 71 regions under the Specified Inhabited Border Islands framework as of April 1, 2025, alongside separate regimes for Okinawa, Amami and Ogasawara. Japan’s total island count in that table is 14,125, of which 417 are inhabited; most islands are uninhabited (MLIT, Measures Taken for Remote Island Development in FY2024 (subcommittee report, Dec. 5, 2025)).

Why Japan also wrote a border-island statute

In April 2016 the Diet passed, as a member’s bill, the Act on Special Measures concerning Preservation of Inhabited Remote Border Islands and Maintenance of Local Communities on Specified Inhabited Remote Border Islands (Act No. 33 of Heisei 28). It took effect in April 2017 (Cabinet Office, Inhabited Border Islands page). The Cabinet Office summarizes the purpose: as the need to manage territorial seas and EEZs grows, inhabited border islands function as hubs for fisheries, ocean surveys and territorial-sea security activities, so the Act provides special measures to preserve those islands and maintain local communities on specified ones (Cabinet Office, Inhabited Border Islands page; Cabinet Office, Act on Special Measures concerning Preservation of Inhabited Remote Border Islands and Maintenance of Local Communities on Specified Inhabited Remote Border Islands (overview PDF)).

The Act’s overview PDF defines inhabited border-island areas as inhabited islands that include territorial baselines (or groups of islands that do), and “specified” inhabited border-island areas as those listed in the Act’s schedule where continuous habitation is especially necessary to maintain the community (Cabinet Office, Act on Special Measures concerning Preservation of Inhabited Remote Border Islands and Maintenance of Local Communities on Specified Inhabited Remote Border Islands (overview PDF)). The Prime Minister sets a basic policy covering, among other items, national facilities, land acquisition, port and airport improvement, prevention of illegal entry by foreign vessels, fare reduction on domestic passenger routes and domestic air services, relief of living and business costs, employment and stable fisheries (Cabinet Office, Act on Special Measures concerning Preservation of Inhabited Remote Border Islands and Maintenance of Local Communities on Specified Inhabited Remote Border Islands (overview PDF); Cabinet Office, Ocean Policy — budgets, systems and related laws).

Cabinet Office notes that a July 2026 (Reiwa 8) amendment was enacted, with the amended text to take effect in April 2027 (Reiwa 9) (Cabinet Office, Inhabited Border Islands page; Cabinet Office, Ocean Policy — budgets, systems and related laws). ISPI reports that schedule as published. The FY2024 measures report states that border-island measures and Remote Islands Development Act measures are closely related and require whole-of-government coordination (MLIT, Measures Taken for Remote Island Development in FY2024 (subcommittee report, Dec. 5, 2025)). For other governments, the institutional point is narrow: Japan separated general remote-island development from inhabited baseline islands that matter for maritime-zone management—and then funded fare and freight relief so communities remain. ISPI does not take sides in territorial disputes; it cites each government’s published position and the statute text.

Ferries, ports and the cost of the last mile

Japan’s published ferry figures make the lifeline problem concrete. As of April 1, 2024, MLIT counted 525 general passenger ferry routes nationwide, of which 276 were remote-island routes linking the mainland to islands or islands to each other; 127 of those remote-island routes were unique-and-deficit routes eligible for subsidy (subsidized count as of Oct. 1, 2024) (MLIT (Shikoku Regional Development Bureau), Remote-island ferry subsidy overview). The FY2025 (Reiwa 7) budget line for remote-island ferry support is ¥7.05 billion, inside a ¥20.9 billion regional public-transport envelope (MLIT (Shikoku Regional Development Bureau), Remote-island ferry subsidy overview).

Subsidy design is explicit. Operating-cost aid covers unique, loss-making routes at up to one-half of standardized deficit; resident fare-discount aid splits the discount cost half with local governments; structural-reform aid supports vessel replacement under public-build/private-operate and similar reforms (MLIT (Shikoku Regional Development Bureau), Remote-island ferry subsidy overview). In FY2024, MLIT reports operating-cost aid to 111 operators on 124 routes, resident fare discounts on 15 ferry routes, structural-reform aid on 13 routes, plus Specified Inhabited Border Islands community-maintenance grants on 31 ferry routes and 20 air routes (MLIT, Measures Taken for Remote Island Development in FY2024 (subcommittee report, Dec. 5, 2025)).

Ports are treated as part of the same lifeline. The Remote Islands Development Act’s basic-policy items expressly include ports (including bridges) among the transport facilities that must be secured (Remote Islands Development Act (e-Gov)). MLIT’s Ports and Harbours Bureau basic policy states that for remote islands and remote areas, maritime transport networks that support daily life and industry are important, that higher ferry sailing rates are needed, and that disaster-resilient ports are required; it calls for facilities that allow efficient cargo handling and safe boarding, calm-water works that raise sailing rates, and berths and fuel-handling capacity that can also serve support vessels after a major disaster (MLIT Ports and Harbours Bureau, Basic Policy on Port Development, Use and Conservation (PDF)).

That is the same single-point-of-failure geometry ISPI describes for Honolulu Harbor in the explainer on Honolulu Harbor and the single-port state, for sister-island ferry recovery in the Hurricane Beryl case study, and for a blocked channel in the Key Bridge and Port of Baltimore channel-closure lessons. Japan’s published answer is to put ferry subsidies, port calm-water works and emergency berth capacity into the same remote-island statute and port basic policy.

Disaster isolation, tsunami warnings and island COOP

MLIT’s FY2024 report states the isolation problem plainly: because remote islands are surrounded by sea, tsunami and similar disasters make evacuation support and recovery slower than on the mainland, and isolation risk is high (MLIT, Measures Taken for Remote Island Development in FY2024 (subcommittee report, Dec. 5, 2025)). Local fiscal measures have been expanded for earthquake and tsunami works that strengthen remote-island disaster functions; soft measures (disaster plans) use the Remote Island Vitalization Grant, and hard measures (evacuation facilities) use the Comprehensive Social Capital Development Grant (MLIT, Measures Taken for Remote Island Development in FY2024 (subcommittee report, Dec. 5, 2025)). FY2024 work included breakwaters, evacuation facilities, emergency power, disaster-administration radio, stockpile warehouses, evacuation routes and hazard-map soft measures; the 2022 Act amendment’s consideration clause references national resilience for advance prevention and mitigation (MLIT, Measures Taken for Remote Island Development in FY2024 (subcommittee report, Dec. 5, 2025)).

Cabinet Office’s Nankai Trough Megathrust Earthquake Countermeasures Working Group overview likewise flags that in mountains, peninsulas and remote islands, communities can be isolated and daily-life effects prolonged, and it lists richer stockpiles and communications among the responses (Cabinet Office, Nankai Trough Megathrust Earthquake Countermeasures Working Group report overview). That is an island COOP assumption: plan for delayed outside help.

Warning time is short. JMA issues Major Tsunami Warnings, Tsunami Warnings and/or Tsunami Advisories for individual forecast regions about three minutes after an earthquake (as early as two minutes in some near-Japan cases) (Japan Meteorological Agency, Tsunami Warning/Advisory and Tsunami Information; JMA, Tsunami warnings, advisories and information (Japanese)). A Major Tsunami Warning applies when expected maximum height exceeds 3 meters (an Emergency Warning); a Tsunami Warning when height is more than 1 meter and up to 3 meters; a Tsunami Advisory when height is 0.2 to 1 meter and tsunami disaster is possible (Japan Meteorological Agency, Tsunami Warning/Advisory and Tsunami Information). For magnitude-8-class events, initial warnings may use “Huge” or “High” until a precise magnitude is available; a near-shore source can bring a tsunami before any warning, so strong or long shaking is itself a cue to evacuate (Japan Meteorological Agency, Tsunami Warning/Advisory and Tsunami Information). Japan pairs that minutes-scale system with remote-island isolation planning, self-sufficient evacuation facilities and stockpiles—the same discipline as the continuity of operations guide for island local government and the household guidance in the World Tsunami Awareness Day guide.

What this means for island and coastal governments

Japan’s ritō framework is not a template to paste onto every SIDS ministry. It is a measured case of how a large archipelagic state wrote remote-island geography into statute, budget and warning systems. Five lessons travel cleanly to other island and coastal governments:

• Name the remote-island estate in law. Japan designates development areas, requires a national basic policy and prefectural plans, and lists transport, medical care, energy and disaster prevention as plan contents (Remote Islands Development Act (e-Gov); MLIT, Remote Islands Development Basic Policy page). Governments that only mention “outer islands” in speeches leave budget and COOP owners unclear.
• Separate development from maritime-zone stewardship if both apply. The Inhabited Border Islands Act adds a second track for inhabited baseline islands and funds fare and freight relief so communities remain (Cabinet Office, Act on Special Measures concerning Preservation of Inhabited Remote Border Islands and Maintenance of Local Communities on Specified Inhabited Remote Border Islands (overview PDF); Cabinet Office, Inhabited Border Islands page). Cite each state’s published position on maritime zones; do not use development law as a proxy for sovereignty claims.
• Treat the ferry and the port as one lifeline. Unique-and-deficit route subsidies, resident fare discounts, vessel-replacement aid and port calm-water / emergency-berth works are published as a single problem (MLIT (Shikoku Regional Development Bureau), Remote-island ferry subsidy overview; MLIT Ports and Harbours Bureau, Basic Policy on Port Development, Use and Conservation (PDF); MLIT, Measures Taken for Remote Island Development in FY2024 (subcommittee report, Dec. 5, 2025)). That matches the single-harbor logic in the explainer on Honolulu Harbor and the single-port state and the supply chain singularity.
• Design for isolation after the wave. MLIT and Cabinet Office texts assume delayed outside help, self-sufficient evacuation sites, stockpiles, emergency power and disaster radio (MLIT, Measures Taken for Remote Island Development in FY2024 (subcommittee report, Dec. 5, 2025); Cabinet Office, Nankai Trough Megathrust Earthquake Countermeasures Working Group report overview). Pair that with JMA-style minutes-scale warning literacy from the World Tsunami Awareness Day guide and with written devolution in the continuity of operations guide for island local government.
• Watch demography as a security input. The Act’s purpose clause and MLIT’s FY2024 report both treat long-run population decline and aging as reasons the special measures exist (Remote Islands Development Act (e-Gov); MLIT, Measures Taken for Remote Island Development in FY2024 (subcommittee report, Dec. 5, 2025)). An empty island cannot run a port, a clinic or a warning siren. Settlement and “related population” measures are resilience tools when they are tied to published plans, not slogans.

Archipelagic peers face the same geometry in different legal clothes—the Philippines 2026 supply-chain singularity case is one recent case. Chokepoint shocks still matter (maritime chokepoints explainer), but ritō policy is about the last mile no foreign carrier will keep open. Japan published how it funds that mile; other governments can read the statutes and decide what to borrow.

Frequently asked questions

What is ritō in Japanese policy?

Ritō means remote islands. Under the Remote Islands Development Act (Act No. 72 of 1953), competent ministers designate remote-island development areas that face severe natural and social conditions compared with other regions. Okinawa, Amami and Ogasawara are covered mainly by separate special-measures laws.

How many islands does the Act cover?

MLIT’s FY2024 report lists 77 regions, 256 inhabited islands, about 5,316 km² and about 340,000 people as of April 1, 2025. MLIT’s page lists 255 islands as of April 1, 2026. Population is from the 2020 census.

What is the Inhabited Border Islands Act?

Act No. 33 of 2016 (effective April 2017) provides special measures to preserve inhabited baseline islands and maintain communities on specified ones, including fare and freight relief. A July 2026 amendment is scheduled to take effect in April 2027.

How does Japan support remote-island ferries?

As of April 1, 2024 MLIT counted 276 remote-island ferry routes; 127 unique-and-deficit routes were subsidy-eligible as of Oct. 1, 2024. FY2025 remote-island ferry funding is ¥7.05 billion, covering operating-cost aid, resident fare discounts and structural-reform support, plus border-island grants.

What should other island governments take from this?

Write remote islands into statute and plans; fund the ferry/port lifeline as one system; plan COOP for delayed outside help; keep tsunami warning literacy at household level; treat depopulation as a resilience risk. Cite each government’s published maritime-zone positions only.

ISPI publishes its research free under CC BY 4.0. If your government, port authority or emergency management agency needs a remote-island exposure review, a ferry-and-port lifeline tabletop or an isolation COOP for an outer island, you can commission research from ISPI. ISPI is a nonprofit organization with its 501(c)(3) application pending.

Sources

1. Remote Islands Development Act (e-Gov)
2. MLIT Remote Islands Development page
3. MLIT, Remote Islands Development Basic Policy page
4. MLIT, Basic Policy for Remote Island Development Areas (PDF)
5. MLIT, Measures Taken for Remote Island Development in FY2024 (subcommittee report, Dec. 5, 2025)
6. MLIT (Shikoku Regional Development Bureau), Remote-island ferry subsidy overview
7. Cabinet Office, Inhabited Border Islands page
8. Cabinet Office, Ocean Policy — budgets, systems and related laws
9. Cabinet Office, Act on Special Measures concerning Preservation of Inhabited Remote Border Islands and Maintenance of Local Communities on Specified Inhabited Remote Border Islands (overview PDF)
10. Japan Meteorological Agency, Tsunami Warning/Advisory and Tsunami Information
11. JMA, Tsunami warnings, advisories and information (Japanese)
12. MLIT Ports and Harbours Bureau, Basic Policy on Port Development, Use and Conservation (PDF)
13. Cabinet Office, Nankai Trough Megathrust Earthquake Countermeasures Working Group report overview
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