Japan just spent $73.6 billion in one month trying to hold the yen up - the most the country has ever deployed in a single month.
The yen still finished May as the worst-performing major currency, with traders stacking more bets on it falling further.
That intervention isn't a small move. Japan sells dollars and buys yen on the open market to prop up its currency, and $73.6 billion is the kind of firepower that usually shifts the tape.
It didn't work.
The spending isn't the core issue. The interest rate gap between Japan and the US is.
The Fed's rates sit well above the BOJ's (Bank of Japan), which makes the dollar a much better place to park cash than the yen. As long as that gap stays wide, every dollar Japan throws at the currency market is fighting against the math.
"Intervention is buying time, not turning the tide," said Masahiko Loo, a senior fixed income strategist at State Street Investment Management. "The real pivot has to come from the BOJ."
Japan dropped a record amount in a single month, and the yen still slid 1.7% in May.
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Big money is betting the yen has further to fall. Short positions among hedge funds and asset managers just hit their highest level in nearly two years, per CFTC data - the US agency that tracks futures market positions - through May 26.
The yen sat at 159.49 against the dollar in Tokyo on Monday, near its weakest reading since the end of April, with many traders eyeing 160 as the next line in the sand.
"The yen could definitely weaken past 160 against the dollar, and then the finance ministry would need to intervene again," said Marito Ueda, managing director at SBI FX Trade.
The war in the Middle East isn't helping either. Oil keeps climbing as US-Iran ceasefire talks stall, and higher oil feeds straight into Japanese inflation - which puts more pressure on the BOJ to act.
The next real test lands on June 16, when the BOJ meets - and rate traders are pricing in a 78% chance the central bank hikes.
If the BOJ moves, intervention gets more effective because the gap with US rates shrinks. If it holds, Japan is back to spending tens of billions to defend a currency the market still wants to sell.
Last week, Finance Minister Satsuki Katayama said the government is ready to step in again if speculators push the yen around.
The market's already daring them to try.
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