The winning bid was placed by the company Kiyomura, whose owner Kiyoshi Kimura runs the sushi chain Sushi Zanmai.
The price was, by a wide margin, a historic record. The previous record of 334 million yen was set at an auction in 2019, which was also won by Kiyoshi Kimura.
After Monday's auction at the Toyosu fish market, Kimura notes that this year's price ended up a little higher than he had expected.
The price went up lightning-fast, he says.
Kimura says he buys expensive tuna to bring luck in his life.
"When I see a beautiful tuna, I can't resist it. I haven't tasted it yet, but it must be delicious," he says of the record-breaking fish, which was caught off Oma in northern Japan.
Prices tend to be especially high during the first auction after New Year celebrations in Japan.
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