Japan spent ¥15.39 trillion in four weeks to hold the yen

Japan spent 15.39 trillion yen, about $96.5 billion, buying its own currency between 30 July and 26 August, the Finance Ministry said on Friday. The sum is the largest monthly yen-buying operation on record. It also lifts this year's total intervention above 27 trillion yen, past the previous annual high of about 15 trillion yen set in 2024.

The ministry published only a period total. A day-by-day split will wait for the quarterly report, expected in early November. Market desks already had a working picture. The Bank of Japan entered the market on 30 July and again on 31 July after the dollar approached 164 yen, the weakest print in about 40 years.

BOJ figures released earlier this month imply that the 30 July session alone may have absorbed as much as 9.6 trillion yen. That would exceed the confirmed single-day record of 6.3 trillion yen from 30 April. The April-May round, during Golden Week, cost 11.73 trillion yen. Friday's number shows the summer round was larger than that entire earlier campaign.

Tokyo and Washington confirmed on 3 August that they had acted together in New York hours on 31 July. Finance Minister Satsuki Katayama and U.S. Treasury Secretary Scott Bessent described it as the first coordinated yen-buying, dollar-selling move in about 28 years. President Donald Trump later called the joint action a signal of friendship. South Korean officials said the Bank of Korea timed its own won purchases with Japan's to add force.

The yen jumped from around 163 per dollar to as strong as 155.20 by 3 August. It then drifted back and has held near 159.50 since 10 August. That is a firmer level than the late-July low, but it is not the floor Tokyo wanted. Import bills keep rising. Japan buys almost all of its energy, and about 95 percent of that energy still comes from the Middle East, where the Iran war has disrupted cargoes through the Strait of Hormuz.

The same cheap yen that lifts Toyota and Sony also inflates household fuel and food costs. The Bank of Japan has tightened policy more slowly than the Federal Reserve, so the interest gap that funds carry trades remains wide. Investors still borrow yen to buy higher-yielding assets elsewhere. Intervention can shock that trade for a few sessions. It does not close the rate gap.

Washington has said Tokyo could tap a COVID-era Federal Reserve swap line if it needed extra dollars to keep intervening. That line matters because Japan's foreign-exchange reserves, large as they are, are not infinite once the monthly bill sits near $100 billion. Traders will watch whether the next quarterly print shows further buying after 26 August, or whether the ministry has paused to conserve firepower.

Prime Minister Sanae Takaichi's spending plans have been cited in market notes as another source of yen pressure. High oil prices compound the same move. The ministry's Friday release does not discuss those politics. It only records how much cash the authorities already spent to keep the currency off a four-decade floor.

The open question is whether 159.50 holds without another large cheque. If it does not, the next intervention will start from a thinner reserve cushion and from a market that has already seen the size of Tokyo's last bid.