Thousands of Japanese have marched to celebrate the last of the country's 50 nuclear reactors being switched off, shaking banners shaped as giant fish that have become a potent anti-nuclear symbol.
Japan will be without electricity from nuclear power for the first time in four decades when one of three reactors at Tomari nuclear plant in the northern island of Hokkaido goes off-line for routine maintenance checks.
After last year's March 11 quake and tsunami set off meltdowns at Fukushima Dai-ichi plant, no reactor stopped for check-ups has restarted amid growing public worries about the safety of nuclear technology.
"Today is a historical day," shouted Masashi Ishikawa to a crowd gathered at a Tokyo park, some holding traditional "Koinobori" carp-shaped banners for Children's Day that have grown into a symbol of the anti-nuclear movement.
"There are so many nuclear plants, but not a single one will be up and running today, and that's because of our efforts," Ishikawa said.
The activists said that it was fitting that the day Japan will stop using nuclear power coincided with the nation's annual Children's Day, because of their concerns about protecting children from radiation, which Fukushima Dai-ichi is still spewing into the air and water.
The government has been eager to restart nuclear reactors, warning about blackouts and rising emissions as Japan is forced to turn to oil and gas for energy.
Japan now requires reactors to pass new tests to withstand quakes and tsunami and needs local residents' approval to restart them.
The response from people living near the nuclear plants has been mixed, with some wanting them back in operation because of jobs, subsidies and other benefits to the local economy.
Before the nuclear crisis, Japan relied on nuclear power for a third of its electricity needs.