Alongside riding every rail line and conquering every airport, I’ve been island-hopping. About 50 islands visited domestically, roughly 80 including overseas.
Japan ranks 7th in the world by number of islands, but not all of them are accessible. Some house military facilities, some are off-limits, and some simply have no means of landing. I visit the ones that are reachable, one by one.
Defining “Island”
The Geospatial Information Authority of Japan (GSI) defines an island (reference) as meeting three conditions:
- Surrounded by a coastline with a perimeter of at least 0.1 km
- Naturally formed
- Not located in inland waters (lakes, river sandbars, etc.)
Under this definition, artificial islands, lake islands, and river sandbars are excluded. However, people live and work on many such places. They’re worth visiting as travel destinations.
My own rule: if it’s surrounded by water and individually reachable, I count it — regardless of the official definition.
Borderline Cases
Looking at maps, there are many places where it’s hard to tell if something qualifies as an island. Some examples from the Kanto area:
- Haneda Airport: Reclaimed land. Runway D is separate but connected by a taxiway.
- Shōwa-jima (Ōta, Tokyo): An artificial island with the Tokyo Monorail depot. Population: 0.
- Ukishima (Kawasaki): Part of an industrial zone. Entirely reclaimed land.
- Uno-shima (Lake Kawaguchi): A natural island in a lake, but excluded under the GSI definition because it’s in inland waters.
Whether to count such places as islands is a matter of personal judgment. I chose to cast a wide net.
Islands Visited So Far
- Myōken-jima (Edogawa, Tokyo): Said to be the only natural island in Tokyo’s 23 wards. A sandbar in the old Edogawa River, now an industrial zone.
- Daini Kaihō (Tokyo Bay): A normally off-limits artificial island. Landing only possible via tour.
- Hateruma Island (Okinawa): The southernmost inhabited island in Japan.
- Rebun Island (Hokkaido): Visited the suspended Rebun Airport.