Residents of Tokyo have been shown a stark warning of what could happen if Mount Fuji erupts.

The metropolitan government released a three-minute AI-generated video depicting the capital buried in volcanic ash to raise awareness and urge preparation.

The simulation shows thick clouds of ash descending on Shibuya and other districts about one to two hours after an eruption, with up to 10 centimetres expected to accumulate. Unlike snow, volcanic ash does not melt away but instead hardens, damages powerlines, and disrupts communications once wet.

The video also highlights major risks to transport. Ash on train tracks, runways, and roads would halt trains, ground planes, and make driving perilous.

Two-wheel vehicles could become unusable under even modest ashfall. Power outages and shortages of food and supplies are expected as shops run empty, echoing the disruption seen after the 2011 earthquake.

Officials advise people to prepare masks, goggles, and at least three days of emergency food. The narrator warns that because no one knows when Mount Fuji might erupt, daily preparedness in Japan is vital to protect health, infrastructure, and communities.