Japan holds 254 days of oil in reserve. That number has been repeated so often since February 28 that it has become a kind of talisman, proof that the country can absorb anything the Strait of Hormuz throws at it. It is also misleading.
On March 16, Prime Minister Takaichi ordered the largest oil reserve release in Japanese history: 80 million barrels, equivalent to 45 days of domestic consumption. The draw came from both private and government stockpiles and was coordinated with a 400-million-barrel IEA-wide release across 32 member nations. Japan’s contribution was the second largest after the United States.
After that release, 209 days remain. That is still the deepest buffer among major economies. Germany is at 76 days. France at 70. South Korea at 49. The UK at 39. Japan is the only IEA member still above the 90-day minimum the agency requires.
The question is not whether 209 days is a lot. It is how fast those days are being consumed.
The three tiers
Japan’s reserve system was built after the 1973 oil crisis and refined over five decades. It has three layers: government-controlled stockpiles (146 days as of December 2025), private-sector mandatory reserves held by refiners (101 days) and joint stockpiles with oil-producing countries (7 days).
The March 16 release drew first from the private tier. The Economy Ministry lowered the mandatory private stockpile requirement from 70 days to 55 days for one month, freeing 15 days of consumption. Government reserves followed with a further 30 days.
The tiers serve different purposes. Private reserves are operationally flexible: they sit in refineries and can enter the supply chain within days. Government reserves are stored in ten coastal bases and require ministerial authorisation and logistical lead time to move. The joint tier, at 7 days, is a diplomatic instrument more than a supply buffer.
What matters now is the burn rate. Japan consumes roughly 3.3 million barrels a day. If Hormuz remains closed and no alternative supply fills the gap, the remaining 209 days of reserves would theoretically last until late October. But reserves are not consumed linearly. The government cannot drain its stockpile to zero. The IEA 90-day floor is a regulatory constraint, and falling below it would signal to markets that Japan has lost its crisis buffer. The real runway is not 209 days. It is the distance between 209 and 90: roughly 119 days, or four months from March 16.
What Hormuz actually cuts
The CSIS analysis of Japan’s exposure is worth reading in full. The headline number: 93% of Japan’s oil imports originate in the Middle East, and 70% of that oil passes through the Strait of Hormuz. The strait has been effectively closed to most commercial traffic since early March. Limited exceptions exist: Iran has allowed some vessels through its own channel north of Larak Island, with passage fees assessed in yuan. Saudi Arabia has rerouted some crude via the East-West Pipeline to Yanbu on the Red Sea. But combined bypass capacity falls far short of normal flows.
The oil picture is only part of the exposure. Japan held roughly 4 million tonnes of LNG in inventory as of early March, enough for about three weeks of consumption. LNG cannot be stockpiled the way crude oil can; it requires cryogenic storage and boils off over time. Qatar, a major LNG supplier, declared force majeure on all exports after Iranian drone strikes hit its facilities.
Then there is the fertiliser chain. Roughly one-third of global fertiliser trade transits Hormuz. Urea prices have risen 50% since the war began. Japan’s agricultural sector imports most of its fertiliser. The food price transmission from energy disruption runs through multiple channels, not just the petrol pump.
The metal nobody expected
Oil dominates the Hormuz narrative. But on March 28, Iran struck the facilities of Emirates Global Aluminium in Abu Dhabi and Aluminium Bahrain (Alba) in Bahrain, the two largest aluminium producers in the Middle East. EGA reported “significant damage” to its Al Taweelah smelter. Alba, which had already cut 19% of capacity due to the Hormuz closure, declared force majeure on deliveries.
The Gulf produces roughly 9% of the world’s primary aluminium. That sounds modest until you consider that the global market was already expected to run a deficit in 2026, and that aluminium smelters, once shut down, take months and substantial capital to restart. EGA and Alba’s combined annual output exceeds 3.2 million tonnes.
Japan is directly exposed. The Gulf accounted for roughly 25% of Japan’s primary aluminium imports last year. EGA and Alba were among the country’s main suppliers; all previously signed contracts have been suspended. Physical premiums in the Japanese market have climbed 30-40% above standard rates as traders scramble for replacement tonnage. On the LME, aluminium hit $3,544 a tonne on March 30, the highest since March 2022, closing in on the all-time record of $4,073.
One Japanese carmaker told industry press that conditions were “extremely turbulent” and projected production cuts within four months if supply constraints persist. Automotive manufacturing runs on rigid specifications; you cannot swap Gulf-grade aluminium for a different alloy without retooling. Japan and South Korea are reportedly exploring purchases from Russian producer Rusal, a sanctioned entity most buyers had avoided since 2022. When supply security collides with sanctions policy, supply security tends to win.
This is not a price story. It is a physical shortage story. Oil reserves can buffer a price spike. There is no strategic aluminium reserve.
The nuclear offset
Each reactor that restarts reduces Japan’s dependence on imported fuel. On February 9, TEPCO restarted Unit 6 at Kashiwazaki-Kariwa in Niigata Prefecture, the world’s largest nuclear plant by capacity and TEPCO’s first restart since the 2011 disaster. The reactor has 1,356 MW of capacity and the US Energy Information Administration estimates it will displace roughly 1.3 million tonnes of LNG imports annually once at full output.
Japan now has 15 operating nuclear reactors with combined capacity of 33 GW, generating about 9% of the country’s electricity in 2024. Three additional reactors are ready for restart. Before the 2011 accident, nuclear provided 30% of Japan’s power from 54 reactors.
The arithmetic is clear: every reactor that comes back online reduces the rate at which oil and gas reserves are consumed. At the current pace, nuclear restarts are adding capacity in single-digit percentage points. A return to pre-Fukushima levels would transform the energy balance. Takaichi has pushed for new reactor construction, and the current crisis strengthens the political case for acceleration.
For the local economy in Niigata, Kashiwazaki-Kariwa’s restart is more than an energy story. The plant brings construction workers, operational staff, tax revenue and supplier contracts back into a prefectural economy that has been shrinking for two decades. The local bank, Daishi Hokuetsu Financial Group, lends into that supply chain. A dormant plant produces zero economic activity for 15 years; a running plant revives an entire credit ecosystem. This is the granular reality beneath the national energy statistics.
The stagflation question
Nissei Basic Research Institute’s chief equity strategist Ide Shingo told Reuters on March 30 that the market was beginning to price genuine stagflation: not demand weakness but supply constraint. Oil above $110 crushes margins for energy-dependent manufacturers. Aluminium shortages halt assembly lines. Fertiliser costs push up food prices. None of this responds to rate cuts.
This is the scenario that traps every central bank, not just the BOJ. Rate hikes contain inflation but deepen the recession. Rate cuts support growth but feed the price spiral. Japan is the canary: it imports 93% of its oil, 25% of its aluminium and most of its fertiliser from regions now under fire. If Japan enters stagflation, it will not be alone. The same supply shock runs through every economy that depends on Middle Eastern energy and Gulf industrial metals. Europe, South Korea, India and Southeast Asia face the same arithmetic at different scales. A Japanese carmaker warning of production cuts in four months is a warning for the global auto supply chain, not just for one company’s shareholders.
The Nikkei has fallen 14% from its February high. Some strategists warn of a further 10-20% decline if the conflict persists. The market is pricing duration.
The yen transmission
Oil reserves do not just buffer physical supply. They buffer the currency. As we wrote in The Carry Trade Ghost, the Hormuz closure creates roughly ¥900 billion a month in additional forced dollar buying by energy importers. Every barrel Japan purchases on the spot market at $116 requires dollars. Every dollar purchased weakens the yen.
Releasing reserves slows this drain temporarily: barrels drawn from stockpiles are already paid for and sitting in Japan. No new dollars are needed. But once the reserves are consumed, the forced dollar buying resumes, and the yen weakening accelerates.
This is the link between the oil clock and the currency. The carry trade ghost article asked whether portfolios were built for a 3% or 10% yen move. The answer depends partly on how long the reserves last. If Hormuz reopens by May, the reserves were never seriously tested and the forced flow stops. If the closure persists into July, Japan is drawing down toward the IEA floor, the forced dollar buying intensifies as spot purchases replace reserve draws, and the yen pressure compounds.
Governor Ueda told parliament on March 30 that failing to raise rates risks destabilising the long end of the JGB curve. But raising rates into an oil-driven supply shock is its own kind of risk. The BOJ is caught between inflation it cannot ignore and an economy it cannot afford to brake. The oil clock is the variable that determines how long this trap persists.
What the clock says
The 254 days that Japan entered this crisis with were the product of 50 years of policy discipline since the 1973 shock. No other major economy built as deep a buffer. That discipline is now being spent, and it cannot be quickly replenished. Refilling strategic reserves after a crisis requires purchasing crude at post-crisis prices on a market that every other IEA member is also trying to restock.
Two paths diverge from here.
In the first, the war persists. Oil reserves grind toward the IEA floor. Aluminium contracts stay suspended. Auto production lines slow and then stop. Forced dollar buying keeps the yen weak. The BOJ is paralysed between inflation and contraction. Stagflation settles in, first in Japan, then everywhere that depends on the same chokepoint.
The market is pricing that path. The Nikkei is down 14%. Energy-dependent industrials are being sold. Automakers are discounting supply chain disruption that has not yet materialised in earnings. The carry trade is rebuilding shorts against the yen. All of this assumes duration.
But wars end. The Hormuz closure has lasted one month. If it ends in another four to five weeks, the forced flows reverse within days. Oil drops back toward $70-80 as reserve releases flood a market that no longer needs them. The forced dollar buying stops. The yen strengthens. Aluminium contracts resume, though smelter damage at EGA and Alba will take longer to repair. The stocks punished hardest for supply chain exposure reprice upward. And the structural trends that preceded the war (rate normalisation, NIM expansion, governance reform, nuclear restarts) resume from cheaper levels.
The first path is on every front page. The second is not. The market is pricing duration, not resolution. Duration is the consensus trade.
We do not know which scenario will play out. But we can observe what the market is paying for each. The equities most leveraged to the first path (defence, oil services, commodity traders) have already moved. The equities most leveraged to the second (automakers with intact balance sheets, banks repricing for higher rates, utilities with restart-eligible reactors, industrials with temporarily disrupted but structurally sound supply chains) are sitting at valuations that assume the disruption is permanent.
If you believe the disruption is permanent, the current prices are fair. If you believe it is not, the arithmetic becomes interesting.
Oil has reserves. Aluminium does not. Reactors take years to build but weeks to restart. The prefectures where those reactors sit are the same prefectures where regional banks have been lending into shrinking economies for two decades. The rate cycle determines what those banks earn on every loan. The oil clock determines how long the BOJ stays trapped between inflation it cannot ignore and an economy it cannot brake.
These are not three separate stories. They are one story, seen from different distances.
Data as of 2026-03-31. Sources: METI oil reserve data via Nippon.com; IEA coordinated release via Al Jazeera; Japan Times (reserve release mechanics); CSIS (Japan exposure analysis); US EIA (Kashiwazaki-Kariwa restart); DropThe (post-release reserve comparison); The National, AL Circle (aluminium supply disruption); S&P Global via The National (Japan aluminium import share).