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Setonaikai NP, Yamaguchi / Fukuoka
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Kanmon links the Sea of Japan side with the Seto Inland Sea. At the narrow Hayatomo Strait, the current can reach about 10 knots (18.5 km/h) and reverse roughly every 6 hours.
The 1185 Battle of Dan-no-ura was the Genpei War’s final sea battle. After the Taira defeat, 8-year-old Emperor Antoku and his grandmother drowned in the strait; nearby Akama Shrine commemorates him.
Shimonoseki often calls fugu “fuku,” echoing the word for good fortune. The Kanmon Strait is one of the city’s fishing grounds; after Yamaguchi Prefecture lifted its fugu ban in 1888, local restaurants and dishes flourished.
Moji’s banana auction began as a quick way to sell overripe fruit from Taiwan before it spoiled. Sellers developed rhythmic 7–5-style patter to draw a crowd; after a wartime pause, local residents revived the tradition in 1976.
On July 1, 1942, the Kanmon Railway Tunnel began cargo service as the world’s first undersea railway tunnel. Passenger trains followed that November, connecting Honshu and Kyushu beneath the strait.
Kanmon port history recounts that Toyotomi Hideyoshi was thrown into the sea when his ship struck a reef in 1592. He survived, but helmsman Akashi Yojihei died by seppuku; a memorial later marked the hazard for passing ships.
A 780-m pedestrian tunnel lets you walk beneath Kanmon Strait from Honshu to Kyushu. At its midpoint, a marker shows where Yamaguchi Prefecture ends and Fukuoka Prefecture begins—a border crossing on foot, below the water.
At peak, about 1,000 vessels pass through Kanmon Strait in a single day. That traffic squeezes through a route whose narrowest point separates the shores by only about 650 m.
In August 1864, 17 British, US, French and Dutch warships attacked Choshu batteries along the Kanmon Strait. The assault followed Choshu’s attacks on foreign ships and blockade of the passage, and helped shift the domain toward opening to foreign powers.
At Shunpanro beside the strait, treaty talks ran in 1895. Li Hongzhang survived an assassin’s shot after the 3rd session, returned to negotiations, and the Treaty of Shimonoseki was signed on April 17, 1895.
Three signal stations report the strait’s current direction, speed and whether it is strengthening or easing. Early stations began in 1909; today’s electronic boards replaced older shape-and-light signals in 1979.
“Kanmon” is a little linguistic bridge: “Kan” comes from Shimonoseki’s 関, while “mon” comes from Moji’s 門. The name brings the towns on opposite sides of the strait together.
