During the interview Tuesday at a Tokyo coffee shop, where he had agreed to talk before continuing on to a poker game with buddies, he explained his recent trades step by step. Dressed in a plain gray T-shirt with a flannel shirt tied around his waist, he was monitoring a brokerage account on his iPad and had a $1,600 burgundy under one arm, a 2003 Domaine de la Romanee- Conti. (It wasn’t a celebratory bottle, he said; he drinks a lot of good wine.)

“Of course I’m happy about today, but you win some and you lose a lot, too,” he said, explaining the Greek financial crisis had cost him about $6 million.

CIS said he has no idea whether or not China is going to drag down the global economy. He doesn’t even care. When he trades, he tracks volumes and price moves to follow the momentum. For him the basic rule is: “Buy stocks that are being bought, and sell stocks that are being sold.”

Latest Trade

The latest trade began on Aug. 12, when CIS noticed a shift in equity markets he hadn’t seen for a while. Shares in the major indexes were struggling to recover from sell-offs. He started shorting Nikkei futures: 200 contracts the first day and another 1,300 over the following week and a half.

The stakes were enormous. With 1,500 contracts at a notional value of about $160,000 each, his bet against the Nikkei was about $240 million. For every 100 yen move in the index, he stood to make or lose $1.25 million.

The market was mostly flat over the next few days; CIS bided his time playing video games. On Friday Aug. 21, the Nikkei dipped. Then on Monday, the index plunged the most in two years, and the futures fell more than 1,000 points to 18,410. By the close at 3 p.m. in Tokyo, his profit stood at about $13 million.

Feedback Loop

This is the point where most traders would take their money off the table and call it a year. Not CIS.

“I’m adding to my position,” he wrote on Twitter. “Then I’m going to go for a walk and prayer.”