To your average punter, much of Bitcoin remains somewhat of a mystery. Even its creator who goes by the pseudonym Satoshi Nakamoto — who is believed to still hold billions of dollars worth of the currency — is not known to the public.
However that hasn't stopped the cryptocurrency from surging in value recently, becoming a mainstream investment frenzy. And at least one major Wall Street bank thinks Mrs Watanabe is behind the digital currency's meteoric rise in price this year.
But who is Mrs Watanabe?
That term (which borrows a common surname in Japan) is actually used to describe the individual Japanese investor, traditionally a housewife who runs the family's finances and became notorious for her involvement in the foreign exchange (forex) market during the country's prolonged recession in the 1990s.
As Time Magazine wrote in 2013: "Penalised by a tax system that didn't encourage their participation in the labour force, many Japanese women found that they could bolster tight budgets by performing online forex trades in between chores and shopping for groceries."
These days the metaphorical Japanese housewife is trying to escape rock-bottom savings rates by investing in the cryptocurrency, or so the theory goes.
Japan accounts for about 50 per cent of global foreign-exchange margin trading, according to Deutsche Bank. But in a note to investors this week, bank analyst Masao Muraki wrote: "We think that retail investors are shifting from leveraged foreign-exchange trading to leveraged cryptocurrency trading."
Forty per cent of Bitcoin trading in October and November was conducted in the Japanese currency yen, according to a Nikkei report cited in the note. In August, CryptoCompare reported Bitcoin trade in Japanese yen accounted for nearly 46 per cent of global trade volume.
The in-vogue digital currency rose more than 60 per cent in May alone when it was reportedly driven higher in part by investors in Japan and South Korea who stepped in as China investment cooled after a central bank crackdown on unregulated digital currencies.
At least anecdotally, the thrill of Bitcoin certainly seems to have intoxicated Japanese retail investors, such as Mutsuko Higo, a 55-year-old social insurance and labour consultant who bought around 200,000 yen ($2,548) worth of bitcoin in March to supplement her retirement savings.
"After I first heard about the bitcoin scheme, I was so excited I couldn't sleep. It's like buying a dream," she told Reuters this week.
"Everyone says we can't rely on Japanese pensions anymore," she said. "This worries me, so I started bitcoins."
But according to Deutsche Bank, it might be more apt to blame Mr Watanabe for contributing to Bitcoin's rise as Japanese men — mostly aged 30-49 — hold 79 per cent of foreign-exchange trading accounts.