While a lot of investors were hitting the panic button Monday, a Japanese day trader who’d made a big bet against the market timed the bottom almost perfectly and narrated a play-by-play of the trade to his 40,000 Twitter followers. He claims to have walked away with $34 million.

As financial markets got crazy this week, many people turned cautious. Some were paralyzed. Not the 36-year-old day trader known by the Internet handle CIS.

“I do my best work when other people are panicking,” he said in an interview Tuesday, about an hour after winding up the biggest trade of a long career betting on stocks. He asked that his real name not be used because he’s worried about robbery or extortion. To support his claims, he shared online brokerage statements showing his trades second by second.

CIS had been shorting futures on the Nikkei 225 Stock Average since mid-August, wagering it would fall. By the market close on Monday, a paper profit of $13 million was staring him in the face. He kept building the position. When he cashed out late that night, a collapse in New York had caused his profit to double.

Instead of celebrating, he kept trading. He started betting the market had bottomed. When he finally took his winnings off the table on Tuesday, he tweeted, “That’s the end of my epic rebound trade.” His profit, he said, had almost tripled.

“It was a perfect trade,” said Naoki Murakami, who follows CIS on Twitter and whose markets blog has made him a minor celebrity in his own right.

Trash Talking

Last year, when he was the subject of a profile in Bloomberg Markets magazine, CIS said that in a decade of day trading, mostly from a spare bedroom in a rented apartment, he had amassed a fortune of about $150 million. At the time, he shared tax returns and brokerage statements to back up his claims. One document showed he had traded $14 billion worth of Japanese equities in 2013 -- about half of 1 percent of all the share transactions done by individuals on the Tokyo Stock Exchange that year.

CIS became a cult figure among Japan’s tight-knit community of day traders by trash talking on Internet message boards early in his career. He’s notorious for lines like “Not even Goldman Sachs can beat me in a trade.” Last year he opened a Twitter account, on which he talks about video games and, regularly, his trading. It’s impossible to say how many of his followers are also day traders, and how many of those buy and sell in his wake. Those who do, of course, are quite possibly helping him make money.

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