Japan and U.S. Joint Intervention Shakes Forex Market: Yen-Shorting Trades Face Headwinds

Strategists indicate that Japan and the United States have jointly intervened in the foreign exchange market, heightening the risks associated with betting on yen depreciation and exerting pressure on Japanese equities. U.S. President Trump stated that the U.S. joined Japan's forex intervention last week, boosting the yen's exchange rate, and described the move as a symbolic gesture of friendship toward Japan. Officials from both countries have indicated that they would not rule out further intervention in the foreign exchange market if necessary.

Jumpei Tanaka, Deputy General Manager of the Foreign Exchange Spot Trading Team at Mizuho Bank, said the joint intervention demonstrates both sides' willingness to take all necessary measures to prevent further yen depreciation, marking a new phase in the foreign exchange market. The upside potential for the USD/JPY exchange rate will be limited.

Masahiro Yamaguchi, Head of Investment Research at Sumitomo Mitsui Trust Bank, pointed out that USD/JPY has fallen below the 200-day moving average of approximately 158 yen, meaning that after a series of interventions, most investors' profits have been erased, and some have even turned to losses.

He noted that the joint intervention by Japan and the U.S. represents a significant shift in the logic of forex market operations for speculative traders. Fundamentally, the yen still faces downward pressure, but speculative trades betting on yen appreciation could obscure this trend.

The key aspect of this action is not Japan's unilateral intervention, but the U.S. also stepping into the market, causing USD/JPY to drop sharply. As traders begin to worry that authorities may intervene again if USD/JPY rises further, betting on yen depreciation has become more difficult.

Gareth Berry, a strategist at Macquarie Group based in Singapore, said Japan's window of opportunity to intervene in the USD/JPY rate is limited, with the goal being to disrupt the exchange rate trend and break key support levels. Neither Japan nor the U.S. has infinite resources, and to succeed, they must quickly change the market's entrenched expectation of a four-year-long upward trend in USD/JPY.

Otherwise, the market might view the recent decline in USD/JPY as a better entry point to reestablish long positions, allowing the original uptrend to resume and missing the intervention opportunity. For the intervention to be effective, the exchange rate trend must be visibly disrupted.

He added that while USD/JPY has broken below the 200-day moving average, more key support levels need to be breached. If the rate fails to fall below 155 yen, the market may perceive that authorities are not truly prepared to take strong measures and could use this hesitation to reposition.

Tsutomu Nakamura, an analyst at Gaitame.com Research Institute, said the market has recognized that both Japanese and U.S. authorities are concerned about yen weakness, reducing the likelihood of a repeat of the excessive depreciation seen before previous interventions. The market backdrop for further yen weakening has clearly changed.

He noted that if authorities intervene again, it would further strengthen the market's perception of policy resolve. However, he still expects the dollar to regain strength after the intervention effect fades, as the U.S. government is unlikely to accept a significant dollar depreciation.

USD/JPY may rebound to around 159 yen, but is not expected to return to pre-intervention highs. If market conditions change, the yen could rise to around 150 yen per dollar by year-end.

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Yugo Tsuboi, Chief Strategist at Daiwa Securities, said the market still struggles to gauge how far the yen could appreciate. The U.S. participation makes this intervention clearly different from Japan's past unilateral actions.

He explained that when Japan acted alone, it was often constrained by the size of its foreign exchange special account and whether the U.S. would allow Japan to sell U.S. Treasury bonds. But with U.S. involvement, there has been a significant change in the scale of funds available and operational convenience, making it difficult for the market to estimate the intervention ceiling. This uncertainty is currently weighing on the Japanese stock market.

Naoki Fujiwara, Senior Fund Manager at Shinkin Asset Management, said yen appreciation has triggered mechanical selling pressure in Japanese equities, although the prior market rally was not primarily driven by yen weakness.

He noted that most Japanese companies assume a USD/JPY exchange rate of around 150 to 155 yen in their financial forecasts, so current exchange rate levels are unlikely to materially impact corporate earnings.

However, since the market still cannot determine how strong a yen appreciation policymakers desire, the timing for buying export-related stocks like automakers remains difficult to judge. Still, he does not expect investors to completely exit Japanese equities at this stage.

Bruce Kirk, Chief Japan Equity Strategist at Goldman Sachs Japan, said in a Bloomberg Television interview that if USD/JPY continues to fall under joint U.S.-Japan government intervention, it would place significant pressure on the stock market, as investors reviewing their portfolios would still see risks from overweight exposure to financial and export-oriented stocks.

Kazuhiro Sasaki, Head of Japan Research at Phillip Securities, said this action helps form a market consensus that 'further yen depreciation is no longer acceptable.' While some benefit from a weak yen, others believe buying Japanese government bonds in a weak-yen environment carries excessive risk.

He noted that the U.S. is highly attentive to the reversal of rising bond yields, and if yields decline, it would hurt bank stock performance.

Whether Intervention Can Reverse the Trend: Market Watches Next Moves by Japan and U.S.

Tony Sycamore, Market Analyst at IG Australia, said historically, joint interventions typically occur only during crises, so the willingness of Japan and U.S. authorities to act together under current conditions exceeded market expectations and reflects stronger-than-expected determination to curb excessive yen depreciation.

Rong Ren Goh, Fixed Income Portfolio Manager at Eastspring Investments, said U.S. participation clearly enhances the credibility of official efforts to stabilize the yen, especially as the market questions whether large-scale interventions are losing effectiveness.

However, the market still lacks clarity on the specific framework of U.S. involvement, including what conditions would trigger further intervention and whether this was merely a one-off response to market volatility.

He noted that more fundamentally, yen weakness reflects long-standing market concerns about Japan's monetary and fiscal policy settings. Without resolving these fundamental issues, intervention alone is unlikely to bring about a sustained reversal.

In terms of market positioning, the possibility of U.S. involvement increases two-way volatility risk, making the yen less likely to depreciate in a stable, predictable manner, thus complicating yen-short trades. While maintaining a cautious view on the yen, the importance of entry price and position sizing has increased.

Gerald Gan, Chief Investment Officer at Reed Capital, said joint Japan-U.S. intervention is unlikely to have a major and lasting impact on yen strength.

He believes forex intervention can only work in the short term and cannot permanently change market sentiment. Even if Japan and the U.S. continue to jointly support the yen, it would be difficult to sustain over the long term, and the effectiveness of intervention would diminish with repeated actions.

The key to a genuine, sustained and significant yen appreciation still lies in policy actions by the Bank of Japan (BOJ).

Charu Chanana, Chief Investment Strategist at Saxo Markets, said the joint intervention has altered the risk-reward structure of short-yen trades in the short term. History shows that authorities often conduct a series of interventions rather than one-off actions, especially when the market quickly gives back initial gains.

She noted the importance of U.S. support lies in transforming intervention from a unilateral Japanese move into a coordinated policy signal between two nations. When both governments are aligned, markets are less willing to bet against policy power.

However, sustained yen strength ultimately requires fundamental support, such as further BOJ rate hikes, declining U.S. yields, or improved Japanese fiscal prospects. Without these factors, intervention may only slow yen depreciation rather than reverse the trend entirely.

She does not believe the yen has entered a long-term bullish phase. The short-term reaction in Japanese equities may be negative, as the market has long benefited from yen weakness, and a rapid reversal naturally suppresses export-oriented firms and earnings expectations.

Pelham Smithers, founder of Pelham Smithers Associates, said inflation concerns are resurfacing in Tokyo markets. While the market's current reaction to government efforts to support the yen is relatively calm, the risk is that this could evolve into a one-way macro fund trade, similar to the 1992 pound crisis.

He warned that if the market perceives government forex intervention as a failure, it could trigger a genuine yen sell-off, further worsening Japan's inflation outlook.