The yen has been front of mind for traders today, with client activity in USD/JPY increasing sharply. Positioning across our client base is, for now, skewed towards short USD/JPY positions, reflecting a broad view that the rally may have become stretched and that a period of mean reversion could follow.

Part of that thinking likely centres on the prospect of another round of intervention from Japan's Ministry of Finance (MOF). Traders remember the intervention on 30 April, when the MOF reportedly spent around ¥11.7 trillion (approximately US$75 billion) supporting the yen. That operation triggered a decline of almost 500 points in USD/JPY, leaving many participants prepared to fade further rallies in anticipation of a similar response.

Instead, today's session delivered the opposite outcome.

USD/JPY broke decisively above the recent highs, triggering stop-loss buying and extending towards 162.40. The question now, is whether the pair can hold 162, and continue to grind higher…

The bigger story extends well beyond today's price action.

The intervention on 30 April represented another unilateral attempt by Japanese authorities to slow speculative selling of the yen. However, many investors increasingly believe the weakness in the currency reflects structural rather than speculative forces.

Repeated intervention has become comparable to holding a ball underwater. Authorities can temporarily suppress the move, but unless the underlying drivers change, the market quickly pushes the exchange rate back towards previous highs.

This explains why many traders now leave limit buy orders several hundred points below the market, hoping any intervention-driven sell-off provides an opportunity to re-establish long USD/JPY positions.

Comments today from Japan's Finance Minister, stating authorities would take "appropriate" foreign exchange measures when necessary, did little to change that perception.

Increasingly, markets believe that any intervention capable of producing a lasting change would require coordination with other major central banks rather than unilateral action from Japan alone.

Perhaps the most powerful force driving USD/JPY higher is the global search for carry.

Carry trades continue to perform exceptionally well as volatility remains subdued, equity markets trade near record highs and investors continue seeking higher-yielding currencies.

The yen remains the preferred funding currency for many global investors.

That is reflected in the performance of popular carry crosses. For example, BRL/JPY has gained roughly 9.5% year-to-date on price alone, with total returns approaching 17% once interest income is included. COP/JPY has delivered even stronger carry-adjusted returns of around 20%.

As long as volatility remains contained and investors remain comfortable taking risk, these carry strategies continue attracting capital.

In that environment, the Bank of Japan is not simply fighting a stronger US dollar. It is fighting one of the most powerful investment themes currently driving global currency markets.

Another factor weighing on the yen is the growing divergence in central bank credibility.

Markets have become increasingly confident in the Federal Reserve under Chair Kevin Warsh, with expectations that policy will remain focused on controlling inflation while supporting economic growth.

By contrast, the Bank of Japan continues to battle perceptions that it has moved too slowly in normalising monetary policy.

Although markets increasingly believe the BOJ will eventually lift policy rates towards a neutral level of around 2%, investors expect that journey to be gradual.

That slow pace continues to undermine confidence in the yen, particularly against a backdrop of Japan's fiscal challenges and elevated public debt.

Capital flows also remain an important structural driver.

Japanese outward foreign direct investment has recently reached around 5% of GDP, among the highest levels on record.

Much of this investment remains unhedged, requiring ongoing purchases of foreign currencies and creating additional selling pressure on the yen.

Those flows could eventually moderate if overseas investment slows, but for now they remain another supportive factor for USD/JPY.

What initially began as a carry trade has increasingly evolved into a momentum trade.

As USD/JPY continues making new highs, systematic funds, trend-following strategies and discretionary traders have steadily increased long US dollar exposure.

The yen has increasingly become the weakest currency within the G10 complex, reinforcing the trend.

That makes intervention increasingly difficult.

Without a meaningful shift in US interest rate expectations, global risk appetite or coordinated international intervention, selling dollars against the yen remains a difficult proposition.

Conditions may evolve after quarter-end portfolio rebalancing, and any surprise from the Federal Reserve or a coordinated policy response could alter the outlook.

For now, however, the market continues to favour buying pullbacks rather than selling rallies.

The combination of positive carry, strong momentum, supportive US interest rate expectations and persistent structural capital outflows continues to outweigh the threat of unilateral Japanese intervention.

Until one of those underlying drivers changes, USD/JPY appears likely to remain supported, even as the risk of official intervention continues to linger in the background.