Overview
Japan’s exit from ultra-low interest rates is turning the yen from a cheap, stable funding tool into a global “risk switch”—a variable whose abrupt movement can quickly change investor positioning, funding costs, and policy responses across markets. Since the Bank of Japan (BOJ) began normalizing policy in March 2024, yen and Japanese government bond (JGB) moves have become more consequential as they now intersect with record-breaking defense spending, alliance management with Washington, and global market stability, with implications for sovereign borrowing costs, cross-border deleveraging, exchange-rate intervention pressure, and alliance coordination. Normalization will increase the likelihood of yen and JGB volatility, raising the risk of carry trade unwinds and global portfolio repricing; because this is unfolding alongside fiscal expansion and diplomatic pressures, “Japan shock” risk is no longer just a domestic macro story but a geopolitical one. In an era of economic statecraft, the yen is now both a market price and a strategic variable that can amplify crises far beyond Japan’s borders.
Japan’s Normalization Is Real
For years, the global economy operated with one unusually stable assumption: borrowing in Japan was cheap and would remain cheap. That assumption is now breaking. Normalization in this instance means the BOJ’s shift away from negative rates and yield-curve control toward a more conventional policy path with positive rates and less direct suppression of long-term yields. In March 2024, the BOJ explicitly judged that its long-standing framework of quantitative and qualitative easing with yield curve control and negative rates had “fulfilled their roles,” and shifted to guiding a short-term policy rate around 0–0.1%. That decision marked a broader transition away from the idea that Japan would remain the world’s source of near-zero financing.
By December 19, 2025, the policy rate had risen to “around 0.75%,” with official communication emphasizing that, if the outlook is realized, the central bank would “continue to raise the policy interest rate and adjust the degree of monetary accommodation.” This is a profound change in both stance and forward guidance. For much of the previous decade, global investors treated Japan as an anchor of stable yields and funding costs. The second-order shift is rising volatility in JGBs, especially at long-dated and super-long maturities. In January 2026, for example, there was a one-day 27 basis-point jump in 30-year yields to a record high of 3.88% amid fiscal concerns tied to election politics and tax cuts—exactly the kind of move that would have been extraordinary under the prior regime. This matters because the BOJ still holds a dominant share of the JGB market while trying to step back from extraordinary support, so sharp price moves quickly raise uncertainty about market functioning, central-bank backstops, and the implications for the yen. A sharp rise in JGB yields raises sovereign financing costs, tightens domestic borrowing conditions, pressures bank balance sheets, and reshapes portfolio allocation. Because Japan is deeply integrated into global capital markets, a repricing of the yen is unlikely to remain contained within Japan.
Security Spending and Fiscal Gravity in a More Dangerous Neighborhood
Japan’s security outlook has hardened since the early 2020s. Its 2022 National Security Strategy describes an international environment of intensifying geopolitical competition and warns that the security environment around Japan is “as severe and complex as it has ever been” since World War II, identifying the growing threats posed by regional military and missile build-ups. The 2022 NSS effectively broke from Japan’s self-defense-only policy, calling for the acquisition of strike-back capabilities and a more offensive role in its alliance with the US.
That strategic backdrop now has direct budgetary consequences. Japan’s five-year Defense Buildup Program (FY2023–FY2027) outlines major defense-capability investments and pegs total expenditure at roughly ¥43 trillion (about $275–$280 billion), breaking from its post-World War II 1% of GDP cap. In parallel, Japan’s political leadership has publicly moved to accelerate defense spending, with Prime Minister Sanae Takaichi pledging to reach a 2% of GDP defense spending goal in the fiscal year ending March 2026, two years earlier than the original FY2027 target. This expanded defense spending also comes against the backdrop of a recent trade arrangement with the United States that includes a commitment to roughly $550 billion (about ¥85 trillion) in investments into the US through 2029.
Taken together, these policies would be difficult to execute under any circumstances, and even harder if paired with the government’s proposed tax-cut commitments from Prime Minister Takaichi’s recent election campaign and newly volatile bond markets, because tax cuts narrow fiscal room just as defense outlays and debt-service costs are rising and markets are scrutinizing Japan’s financing path more closely. In a higher-rate environment, investors become more sensitive to how long-term defense outlays and other fiscal promises will be financed in a country that already carries very high public debt. Japan’s Ministry of Finance projects long-term debt outstanding (central and local governments combined) at roughly ¥1,330 trillion, or 211% of GDP, at the end of FY2025, and its fiscal projections suggest annual bond issuance may need to rise to about ¥38 trillion in fiscal 2029 (from ¥29.6 trillion in fiscal 2026), while debt-service outlays could reach roughly ¥40.3 trillion, or about 30% of total public spending. The strategic implication is that fiscal credibility becomes part of deterrence capacity: when financing costs rise and market confidence weakens, Japan’s freedom of action narrows during crises.
Currency Diplomacy and Politics Turn Foreign Exchange Markets into a Policy Battlefield
Washington and Tokyo have increasingly formalized language on when currency intervention is justified. A joint US-Japan statement published in September 2025 reaffirmed a commitment to market-determined exchange rates while explicitly noting that “excess volatility and disorderly movements” can harm stability, and that intervention should be reserved for combating such volatility. That language matters because it shapes expectations about what each side may tolerate and whether coordination is possible in a crisis.
Japanese officials are also discussing yen movements in more explicitly political terms. In January 2026, Japan’s finance minister, Satsuki Katayama, said she and her US counterpart, Scott Bessent, shared concerns about what she called the yen’s “one-sided depreciation,” while also pointing to the September joint statement as a foundation for Japan’s “free hand” against excessive moves. US Treasury messaging has likewise emphasized the undesirability of excessive exchange-rate volatility and the importance of sound monetary-policy formulation and communication, linking yen stability directly to central-bank behavior. Once currency swings become a recurring political problem—raising import costs, squeezing households, or prompting accusations of unfair advantage—exchange rates cease to be a background market variable and become part of bilateral bargaining, alongside tariffs and industrial policy.
Foreign exchange (FX) reserves have also become entangled in domestic fiscal politics. Those foreign-currency assets (largely US Treasuries) give Tokyo credible capacity to stabilize the yen in disorderly conditions. Debate is increasing over tapping this roughly $1.4 trillion “war chest” to ease fiscal pressure, but this could introduce further volatility risk for the yen and undermine the purpose of strong foreign reserves: to preserve intervention capacity and market confidence during disorderly currency moves.
How the Yen Flips from Funding Tool to Shock Amplifier
The yen has long been used for carry trades: when investors borrow in a low-interest-rate currency and invest in higher-yielding assets elsewhere. That structure supports risk-taking in calm periods but can amplify stress in volatile ones. When the yen strengthens sharply, borrowers with yen liabilities must buy yen back at a worse exchange rate to repay funding. If the return on foreign assets no longer sufficiently exceeds the cost of yen borrowing, investors close positions to avoid losses. That can force rapid selling of the assets purchased with yen funding, sometimes across multiple markets at once. At scale, this becomes deleveraging: investors reduce borrowed exposure quickly, often by selling whatever is most liquid. For example, if rising yen funding costs or a sharp yen appreciation make yen-funded positions in US Treasuries unprofitable, investors may unwind those trades by selling Treasuries, pushing bond prices down, yields up, and potentially raising US borrowing costs. This is how Japan’s yen volatility could create knock-on effects for foreign markets.
This mechanism is not theoretical. The Bank for International Settlements described an episode in August 2024 in which Japan became “a locus of turbulence”: leveraged positions, “above all carry trades,” came under pressure; the yen appreciated sharply; Japan’s stock market sold off; and the currency repricing reverberated globally as the VIX, a volatility index, spiked.
Carry trade stress is only part of the story. The JGB market itself is becoming more globally sensitive as foreign investors and leveraged funds play a larger role in trading and price formation. The BOJ’s October 2025 Financial System Report notes that foreign investors, including hedge funds, have significantly increased transaction volume in JGB markets, and that hedge funds have been increasing leverage, especially through repo financing (repurchase agreements). It warns that rapid position adjustments and deleveraging can amplify government-bond volatility, spill into a wide range of Japanese financial instruments, and transmit shocks internationally through globally active funds.
Implications for Global Geopolitics and Economic Stability
Japan’s normalization creates a new policy problem: yen moves can now disrupt both domestic politics and alliance management. A weaker yen raises import costs and household pressure in Japan, while a sudden risk-off appreciation can trigger rapid asset sales, tighten global financial conditions, and make crisis management harder when governments most need stable markets. Security-driven fiscal expansion adds a second constraint. With debt already high, even modest increases in long-term yields can carry outsized political and strategic consequences. Alliance politics now sits directly atop these market mechanics. The yen’s sharp moves amid reports in January 2026 of New York Fed rate checks and Japanese references to close US coordination illustrate how sensitive markets have become to even tentative signals of policy alignment. A destabilizing yen move or JGB selloff would not just raise financing costs in the abstract; it could complicate Japan’s ability to sustain defense procurement and other long-horizon deterrence investments on politically acceptable terms.
A practical way to map the risk is to ask where strain would appear first if the yen “flips.” Three early-warning arenas stand out. The first is FX itself, especially sharp, one-sided USD/JPY moves that trigger intervention rhetoric or action. The second is the super-long end of the JGB curve, where fiscal and political shocks have already produced outsized daily moves and where policymakers face difficult tradeoffs between stabilizing bonds and managing the currency’s signal value. The third is cross-border transmission through leveraged positioning and globally active funds: both the BIS and the BOJ have explicitly described how carry trade stress and hedge-fund deleveraging can amplify volatility and transmit shocks internationally.
Japan still has substantial buffers—notably the BOJ’s market footprint and large FX reserves—but they do not eliminate the policy problem created by normalization. Instead, they raise the stakes of official signaling, intervention decisions, and bond-market management at moments of stress. The key issue is no longer whether yen and JGB volatility matter only inside Japan, but whether Tokyo and Washington can manage those shocks without undermining financing confidence, deterrence planning, or market stability. That is what makes Japan’s monetary transition a geopolitical issue, not merely a financial one.
