Oshima Joins Chiba and More as Typhoon Dujuan Unleashes a Powerful Rain and Travel Crisis Across Japan

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Typhoon Dujuan has put parts of Japan into a serious travel and safety crisis. The storm, known in Japan as Typhoon No. 25, brought huge rain, fierce wind and wild seas to the Izu Islands and the wider Kanto region on 20 and 21 September 2026. The hardest-hit place was Oshima Town on Izu Ōshima, an island south of Tokyo.
Japan’s weather agency issued its highest Level 5 warning for landslides in Oshima Town. This alert means that a disaster may already be happening. It tells people in danger areas to take immediate action to save their lives. It was not a normal rainy-day warning. It was the strongest possible warning for ground collapse caused by rain.
The Japanese government also placed Oshima Town under the Disaster Relief Act. This step allows emergency help to reach people quickly. It shows that officials saw a real threat to life and safety. Weather support teams were sent to the island as the storm moved close.
Dujuan did not only bring rain. It brought a long period of wet weather before its closest approach. That made the ground weak. Hillsides can break after days of heavy rain because the soil becomes full of water. This is why Oshima faced such a high landslide risk.

Record rain turns a storm into a wider disaster test

The rain totals show why the danger grew so quickly. From 19 September, the Izu Islands received more than 800 millimetres of rain. Shizuoka Prefecture received more than 500 millimetres. Chiba Prefecture received more than 450 millimetres.
These are very large totals for only a few days. Rain this heavy can fill rivers, flood roads and send mud down slopes. It can also stop people from travelling, even when a city does not suffer major building damage.
The storm moved north-east south of the Bōsō Peninsula. It brought its strongest weather to the Pacific side of eastern Japan. Officials warned that powerful rain bands could form. These narrow bands can drop huge amounts of rain over one small area in a short time. That makes local flooding and landslides much more dangerous.
Oshima Town was the main life-safety emergency. But Chiba became the main mainland story. The prefecture saw flooding, landslides, damaged homes, road closures and transport trouble across a large area.

Chiba faces the widest mainland impact

Japan applied disaster-relief measures to 24 places in Chiba Prefecture. The list included Chiba City, Chōshi, Kisarazu, Narita, Asahi, Katsuura, Kamogawa, Kimitsu, Futtsu, Sodegaura, Minamibōsō and Isumi, as well as several towns and Chōsei Village.
This does not mean every place suffered the same damage. It means the government saw serious danger or a need for support across a wide part of the prefecture.
Chiba City had a water problem after pipes were damaged. Five connections lost water, and emergency water supplies began. The Muratachō underpass on Route 16 also closed because of the heavy rain risk.
In the Kimitsu area, the Koito River reached the highest flood alert level. Cameras confirmed flooding. This is a key warning sign because it means water had already escaped into nearby areas or caused serious risk.
Chiba also reported eight landslide incidents by early evening on 21 September. Officials recorded two homes destroyed, one home badly damaged and one home partly damaged. The official report did not name the exact towns where these home losses happened. This is important. News reports must not guess the location of damage before local authorities confirm it.
Futtsu and Minamibōsō faced road closures. Parts of Route 127 shut because of rain. The Bōsō Peninsula road network also faced expressway closures. Travel through Kisarazu and Sodegaura became harder when the Tokyo Bay Aqua-Line Link Road closed in places because of strong wind and heavy rain.

Tokyo and Kanagawa see major disruption

Tokyo was not the centre of physical destruction. Still, the storm disrupted daily life and travel across the capital region. Hachijō Island faced bad weather as the wider Izu Islands came under pressure. In Tachikawa, Showa Kinen Park closed for safety checks.
Kanagawa also saw damage and closures. Kamakura reported damage to a rainwater-channel bank, though workers completed emergency repairs. In Yokohama, an underground car park closed after rainfall passed safety limits. Roads around Yokosuka and the Miura Peninsula also closed in places.
These impacts show why typhoons affect more than homes. A closed road can stop workers, tourists, food deliveries and emergency teams. A closed rail line can leave travellers stranded far from where the worst rain falls.

Flights ferries trains and parks shut down

Dujuan caused major travel chaos across Japan’s east. Airlines cancelled 384 flights on 21 September, mainly on services linked to the Kanto region. Rail companies suspended 37 local lines. The JR East Uchibō Line in Chiba had debris and mud between Anegasaki and Nagaur­a stations.
Ferries also stopped. Twenty-nine operators suspended services on 34 routes. This was especially serious for islands and coastal communities, where ferries are a daily lifeline.
Visitor sites felt the impact too. National parks and public attractions in Hitachinaka, Ōiso and Tachikawa closed for safety checks. The Asian Games in Aichi also postponed equestrian eventing because of the approaching storm.

Cities and Areas of Japan Affected by Typhoon Dujuan

The real lesson from Dujuan

Typhoon Dujuan shows how one storm can create very different risks across Japan. Oshima Town faced the most urgent threat to life from landslides. Chiba faced the widest mainland disruption, with floods, road closures, damage and water problems. Tokyo, Kanagawa and Shizuoka saw serious travel and infrastructure pressure.
The story is not only about wind and rain. It is about what happens when rain falls for days before a typhoon arrives. The ground becomes weak. Rivers rise. Roads close. Travel stops. For visitors and residents, the safest choice is to follow local warnings early and never wait until danger is visible.