Indeed, online currency trading has become a phenomenon here, with a subculture of blogs, books and investing clubs for Japan’s legions of housewife-traders. The appeal, many of these women say, lies partly in the potential that online trading offered at least some financial independence for wives who still wanted to dutifully spend their days at home.

Some of the women used their own money, some used their husband’s, and some used a combination of both. But by trading, they challenged deeply held social prohibitions in Japan against money, which is often seen here as dirty, especially when earned through market speculation.

“There are strict taboos against money that isn’t earned with sweat from the brow,” said Mayumi Torii, a 41-year-old mother of one who said she earned $150,000 since she started margin trading in currencies early last year.

Ms. Torii is one of Japan’s most famous housewife-traders. She has written a book on her investing strategies and founded a support group for home traders, the FX Beauties Club, which now has 40 members. (FX is financial shorthand for “foreign exchange.”)

But until her book was released in July, she said, she was afraid to admit even to her friends that she was trading, though her husband knew and approved. Now she is a regular guest on television programs.

Ms. Torii said she intended to keep trading, despite the recent market setbacks. She said it was her best chance to “stand on my own economically,” a necessity she discovered after her first marriage ended in divorce, and she and her son had to live off her meager savings. “I never want to feel that vulnerable again,” said Ms. Torii, now remarried.

For other women, trading offered a more modest sort of independence, giving them a chance to build up savings separate from their husbands’ accounts.