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Fuji-Hakone-Izu NP, Shizuoka
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The islands bend and weaken incoming waves; calmer water from both sides meets and piles up a stone bar, exposed only at low tide. Shizuoka designated this wave-built natural feature a Prefectural Natural Monument in 1983.
These islands are the exposed plumbing of an ancient seafloor volcano: cooled magma shrank into columns. On Elephant Island (象島), also called Denbei Island (伝兵衛島), the rock pattern makes a striking elephant-like shape.
Local legend says a Genji youth called Izu no Sanshiro hid on Nakano Island. In 1180, Koyuki, daughter of local leader Seo Yukinobu, was swept away while crossing the rising tide with news of Yoritomo’s uprising.
The sea around Sanshiro has yielded tengusa, a red seaweed boiled into tokoroten—cool, springy noodles. Each May, Nishiizu marks the harvest with free servings and hands-on tokoroten pressing.
Sanshiro-jima is a group of 4 islands—Denbei (伝兵衛島), Nakano (中ノ島), Okinose (沖ノ瀬島) and Takashima (高島)—but from some angles only 3 are visible. The Izu Peninsula Geopark gives this changing count as the name’s explanation.
Local fishers and dive shops removed about 23,000 purple sea urchins around Sanshiro in fiscal year 2025. By February 2026, tengusa had begun growing on formerly bare rock; Shizuoka researchers say the removals may be helping.
Each spring, Nishiizu marks the season with a beach cleanup, group crossing, naturalist-led tide-pool lesson and candy toss for children—a cheerful welcome for a sea road the tide lends for only a short time.
The newly exposed stone route also reveals little tide pools: park rangers have spotted small fish and shellfish tucked among the rocks. Crossing the sea can turn into a miniature wildlife hunt.
