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Fuji-Hakone-Izu NP, Tokyo
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About 38,000 years ago, people carried Kozushima obsidian across 30–40 km of sea to Honshu. Chemical fingerprints in mainland tools point back to the island—a rare trace of Paleolithic seafaring.
In 1787, Kozushima paid part of its tax in dried bonito, not rice. Each August 2, its shrine ritual turns the courtyard into a fishing ground: bamboo boats race while sweets fly as bait for the “katsuo” crowd.
Kozushima’s flat crown is eruption-built: in 838, pyroclastic flows and surges came first, then the Tenjo-san lava dome formed. The eruption left about 1 km³ of deposits, most now underwater.
Sweet potato once served as Kozushima’s staple. Islanders turned it into aburaki—boiled tuber kneaded with starch and flour, then fried—and kiriboshi mochi, a dried-potato-and-rice treat for celebrations.
The entire 18.58 km² Kozushima municipality—not just one viewpoint—earned Dark Sky Park status in 2020. Residents replaced more than 400 road and streetlights with less-glary fixtures to protect the stars.
Legend says the Izu Islands’ gods met on Tenjo-san to divide precious water. When the late-arriving god of Toshima found little left, he leapt into it in anger; the splash became Kozushima’s many springs.
Rain quickly drains through many volcanic islands, but Kozushima is unusually spring-rich: water filters through pumice and ash layers, then emerges to supply homes, local shochu and craft beer.
Meet the Mikura-miyama stag beetle: under 5 cm long, flightless, and it doesn’t feed on tree sap. It occurs naturally only on Kozushima and Mikurajima, and collecting it is prohibited.
At just 572 m, Tenjo-san has treeless summit patches where forest would usually grow. Its 838 eruption, geology and weather help keep trees at bay, while seasonal flowers thrive.
On offshore islets belonging to Kozushima, including Onbase and Tadanaejima, Japanese murrelets breed alongside other seabirds. These protected nesting grounds are out at sea, not on the main island.
Kozushima’s volcanic beaches can be strikingly white: silica-rich rhyolite forms pale sand, while basalt-built Izu islands often have dark shores. The contrast begins in the island’s bedrock.
At Awa-no-mikoto Shrine, “shiobana” is no bouquet: it is wet shore sand set on a flat pebble. Islanders offer it for a good catch or safe departure, treating sea sand and stones as vessels for kami.
Kozushima’s 100 Kannon stones recreate 3 famous pilgrimage circuits—Saigoku, Bando and Chichibu—so islanders could honor all 100 sites close to home. Such combined island circuits are unusual in Japan.
Kozushima’s home-style shoyu meshi mixes rice with rockweed, soy sauce and oil, often with a little sticky rice. It isn’t just a festival dish: households enjoy it in everyday meals, too.
Until the 1950s, Kozushima’s Nijugonichi-sama observance meant work stopped on lunar January 24–25: people shut their shutters, extinguished lights and stayed indoors, believing a visiting deity roamed at night.
Both of Tokyo’s shrines classified as Myōjin Taisha stand on Kozushima: Monoi-mina and Awa shrines appear in the 927 Engishiki register, an old court catalogue of shrines.
A 9th-century court chronicle gave the 838 eruption a divine backstory: it said goddess Awa was angered when her rival received court rank first. That is the chronicle’s sacred-era explanation, not a geological cause.
