The battered nuclear plant at Fukushima, where radioactive water is leaking into the ocean, hangs over Tokyo's bid for the 2020 Olympic Games.
The shadow it casts loomed even larger on Wednesday when a powerful earthquake rattled the Japanese capital, reinforcing worries at home and abroad about safety.
The 6.5-magnitude earthquake hurt no one and caused no damage -- Tokyo has some of the best quake-proofing in the world -- and the operator of the nuclear plant, Tokyo Electric Power, was quick to say there was no new damage.
About 600 households lost power Wednesday, however for around three hours after a tornado ripped through Yaita city, said Tokyo Electric Power. The city is located about 100 kilometers (60 miles) north of Tokyo.
The winds came after tornadoes injured 63 people and damaged or destroyed 110 houses in other parts of eastern Japan on Monday, with a large amount of damage in Koshigaya city, northwest of Tokyo.
But just two-and-a-half years into what could be a four-decade clean-up, the nuclear disaster sparked by the 2011 Tōhoku earthquake and tsunami is very much the Achilles heel of Tokyo's efforts to bag the Games.
Olympic chiefs meet in Buenos Aires on Saturday to choose between Tokyo, Madrid and Istanbul.
Supporters of Japan's bid -- chief among them Prime Minister Shinzo Abe -- insist the plant, 220 kilometers (130 miles) north of the city, poses no danger to athletes or spectators.
"Voices of concern have been raised about the waste water problem in Fukushima," said Abe, referring to a series of leaks of radioactive water, some of which has made its way into the sea.
"The government will stand at the forefront to completely fix this problem. I want to explain that this is not going to be a problem in any way in seven years' time," he said.
The Japanese government has argued that a 2020 Tokyo Olympics would inspire the world by showcasing how Japan has recovered from the triple catastrophe of March 2011.
Japan's northern Pacific coastline was hit by a 9.0-magnitude earthquake, unleashing a towering tsunami that killed more than 18,000 people.
Cooling systems at Fukushima Daiichi nuclear plant were swamped. Reactors went into meltdown and spewed radioactive materials over a tract of prime farmland.
Tens of thousands of people were evacuated from their homes; many are still unable to return.