For months, the yen needed help. Now it may be moving on its own. The Japanese currency has strengthened through ¥155 per dollar, triggering stop-loss orders and pushing USD/JPY towards the ¥152 area, its strongest level of the year. The yen is already up around 4% this month, making it the best-performing G10 currency. The important development is not the magnitude of the move. It is its origin. Governments created the first phase of the yen recovery. Tokyo spent heavily to defend the currency, and Washington joined the effort, sending a clear message that an uncontrolled slide toward ¥165 would not be tolerated. That intervention changed positioning. It did not change the fundamentals. This time may be different.

Markets now assign roughly a 97% probability to a 25-basis-point Bank of Japan rate increase at its September meeting. Policymakers are also beginning to suggest that one hike may not necessarily be the last. That matters because the yen’s weakness was never simply a currency problem. It was an interest-rate problem. For years, investors could borrow in Japan for almost no cost and invest elsewhere. The US, Europe, Australia and emerging markets all offered significantly higher returns. The yen became the world’s funding currency. As long as Japanese rates remained close to zero, selling yen was not simply speculation. It was an economic strategy. The BOJ is now beginning to challenge that strategy. A 25-basis-point increase alone will not eliminate the rate differential with the United States. But markets do not wait for differentials to disappear. They trade the direction. If Japanese rates are rising while the Fed nears the end of its tightening cycle, the expected return from borrowing yen becomes less attractive. Then positioning starts to matter. The break through ¥155 triggered stop losses and forced option dealers to sell dollars. Short-yen positions accumulated after earlier intervention are being reduced. Yen strength has also spread beyond the dollar into the euro, sterling and Australian dollar. That is significant. This is no longer simply a weak-dollar story. It is increasingly a strong-yen story. Currency moves become much more powerful when fundamentals and market mechanics push in the same direction.

The next level is obvious. Around ¥152 lies the yen’s strongest point against the dollar this year. Breaking it would do more than establish another technical milestone. It could accelerate the unwinding of the carry trade. Carry trades remain stable as long as investors believe the funding currency will stay weak. Once it begins appreciating rapidly, the economics reverse. The investor no longer simply worries about earning less carry. He starts losing principal through the currency. That forces positions to close. Closing them requires buying yen. The yen rises further. More positions become unprofitable. More are closed. What began as monetary policy can therefore become a positioning event. This is where Japan could again matter for global markets. Decades of exceptionally cheap Japanese money encouraged investors to finance positions across bonds, equities and currencies internationally. A sustained appreciation of the yen would increase the cost of maintaining those positions and could force some investors to reduce leverage.

The risk is not necessarily a dramatic global liquidation. It is a change in the marginal buyer. Japan is also entering a period when domestic yields are becoming more attractive. If Japanese investors can earn materially higher returns at home while the yen strengthens, the incentive to add foreign exposure weakens. That matters well beyond FX. But there is one condition. The BOJ must now validate what markets have begun to price. A September increase has become almost expected. Simply delivering it may no longer be sufficient. The signal about what comes next will matter more. If Governor Kazuo Ueda suggests that further tightening remains realistic, the market will conclude that Japan is finally leaving its exceptional monetary regime. If he emphasises patience and pushes back against additional increases, investors may rebuild short-yen positions and USD/JPY could return towards ¥155. The meeting is therefore less about 25 basis points than about credibility. The intervention phase has already done its work. It broke the conviction that the authorities would tolerate unlimited yen weakness.

The current rally is doing something more important. It is breaking the conviction that selling the yen remains structurally profitable. That is a much larger change. Governments can force a currency higher for a few days. They cannot sustain it indefinitely. Fundamentals have to take over. For the first time in years, they may finally be. The yen no longer needs Tokyo to buy it. The market has started buying it itself.

The consequences for the dollar could be more important than the bilateral move itself. A sustained yen recovery would remove one of the strongest structural supports behind US dollar demand: the persistent US–Japan interest-rate gap. As hedging costs fall and Japanese investors become less willing to remain fully exposed to dollar risk, part of the enormous stock of US assets held abroad could increasingly be currency-hedged rather than sold. That distinction matters. The Treasury market may keep the capital while the dollar loses the flow. A stronger yen would also reinforce the perception that the global rate cycle is becoming less US-centric, reducing the dollar’s relative yield advantage. If that process coincides with concerns over US fiscal policy and Washington’s efforts to contain long-term yields, the pressure could extend well beyond USD/JPY. The yen would not simply be recovering. It could become another channel through which the dollar’s broader overvaluation is unwound.