Resumption of "Reverse Blockade" in the Strait of Hormuz: The Impact of Rising Oil Prices and 20% Transit Fees on Japan

The U.S. Reinstates "Iran's Sea" Blockade

The U.S. has announced the resumption of a maritime blockade against Iran, rapidly escalating tensions surrounding the Strait of Hormuz once again.

President Trump has reinstated the blockade on Iranian vessels, positioning the U.S. as the "guardian" ensuring the safety of the Strait of Hormuz. He also expressed the intention to impose a burden equivalent to 20% of the value of cargo passing through the strait.

However, the term "blockade" here does not mean stopping all ships navigating the Strait of Hormuz indiscriminately.

According to a navigation warning issued by the Joint Maritime Information Center led by the U.S. Navy, the blockade targets vessels entering and exiting Iranian ports, oil terminals, and coastal areas. It is explained that the passage of neutral ships destined for countries other than Iran will not be hindered in principle.

However, "being able to pass" is not the same as "being able to operate safely as usual."

In the targeted sea area, calling out to ships, inspections, searches, course changes, and seizures are anticipated, and ships that do not comply with orders may face enforcement measures. If U.S. warships and Iranian Revolutionary Guard vessels, small fast boats, drones, and coastal missile units face each other in the narrow sea area, there is a risk of misidentification or communication errors quickly escalating into military conflict.

Thus, the issue at hand is not a simple binary choice of "whether the strait is completely closed or open."

What is crucial for actual shipping is whether shipping companies can tolerate the risks, whether they can board crew members, whether insurance companies will underwrite, and whether shippers can bear the surcharge. Even if legally passable, if tankers refrain from navigating due to insurance premiums or safety reasons, a state close to an economic blockade could arise.

Why Hopes for a Ceasefire Were Dashed

In June, a memorandum aimed at easing tensions was signed between the U.S. and Iran, raising expectations for the recovery of maritime traffic.

However, attacks on ships, military actions by the U.S. and Iran, and disputes over control of the strait continued. The U.S. claims that "Iran threatened the safety of merchant ships," while Iran rebuts that "the U.S. is violating sovereignty and security."

The conflict between the two countries has evolved beyond simple navigation safety into a power struggle over who dictates the order of the Strait of Hormuz.

For Iran, the strait is a lifeline for security adjacent to its coast and one of the few strategic cards it can wield even under sanctions. For the U.S., not allowing a single country to control an international route that influences global energy supply is directly linked to promises to allies and military prestige.

In this structure, neither side can easily back down.

If the U.S. strengthens its escort and blockade, Iran may counter with surveillance, warnings, route designation, and approaching ships. If Iran obstructs passage, the U.S. may increase pressure, including airstrikes and seizures.

Both sides claim that "the other broke the order first," making compromise politically difficult domestically.

Questions Raised by the "20% Cargo Value"

What particularly stirred the market and social media was President Trump's proposal of a 20% burden.

The idea is to receive compensation based on the value of passing cargo in exchange for providing security for the strait, but the implementation method and legal basis are unclear.

The right of ships to pass through international straits is not something coastal or third countries can freely charge for. The International Maritime Organization has also expressed a negative stance on imposing de facto transit fees for international straits.

Even if changed to a form of burden for security services, issues remain regarding who collects it, which cargo is assessed, and how to handle ships that refuse.

Moreover, the 20% figure is incomparable to the usual levels of port usage fees or insurance premiums.

Applying a uniform percentage to the value of cargo such as crude oil, LNG, petroleum products, chemical raw materials, and container cargo is closer to a de facto tariff than a transportation fee. Even if the full amount is not collected, the market incorporates the "possibility of additional burdens" into prices.

Shipping companies add a risk area surcharge to contracts, insurance companies raise war risk premiums, and shippers look for alternative routes and procurement sources. These costs are ultimately passed on to product prices.

The U.S. is believed to aim to exclude Iran's influence while also having users of the strait bear the cost of its defense.

However, if the fee proposal proceeds without sufficient coordination with allies and Gulf countries, the noble cause of "protecting freedom of navigation" may clash with the impression that "the U.S. is monetizing the strait."

As a result, it may not weaken Iran's claims but rather broaden opposition to the U.S.

The Oil Market Has Already Reacted

In response to the renewed tensions, oil prices have surged.

At the time of reporting, North Sea Brent crude oil rose to around $85 per barrel, recording significant gains the previous day. The market fears not only a decrease in Iranian oil exports.

It also fears disruptions in the transportation of oil and LNG from Gulf countries such as Saudi Arabia, the United Arab Emirates, Kuwait, and Qatar, as well as tanker shortages and rising insurance premiums driving up global supply costs.

The Strait of Hormuz is not just a narrow Middle Eastern sea route. It is one of the largest chokepoints in the world's oil supply and is particularly important for energy transportation to Asia.

If transit volume through the strait decreases, Asian importing countries such as Japan, China, South Korea, and India will be more strongly affected than the West.

In Japan, the rise in oil prices is amplified by the yen exchange rate.

If dollar-denominated oil prices rise and the yen depreciates simultaneously, import prices will increase doubly. This affects not only gasoline and diesel but also aviation fuel, power generation fuel, plastics, synthetic fibers, fertilizers, paints, and pharmaceutical raw materials, all of which originate from oil.

Japan's Greatest Weakness is "Concentration" Rather Than "Quantity"

Japan imports almost all of its crude oil, with over 90% dependency on the Middle East.

According to the Agency for Natural Resources and Energy, Japan's crude oil imports in 2024 are expected to be about 2.36 million barrels per day, with over 90% dependence on the Middle East. Moreover, most Middle Eastern crude oil passes through multiple chokepoints, including the Strait of Hormuz and the Strait of Malacca.

Japan has national reserves, private reserves, and joint reserves with oil-producing countries, so gasoline will not immediately run out domestically.

Even in crises beyond spring 2026, the government has been advancing reserve releases and alternative procurement. It is possible to procure crude oil from the U.S., Africa, and Latin America, and some Gulf oil-producing countries have pipelines and ports that can export without passing through the Strait of Hormuz.

However, there is no room for complacency.

Reserves are a system to buy time, not a permanent supply source. Alternative crude oil differs in quality, and domestic refineries may not process it with the same efficiency. Long-distance transportation reduces ship turnover rates and increases freight costs.

Furthermore, even if crude oil is secured, shortages of individual products such as naphtha, LPG, and petrochemical raw materials may surface first.

The impact on the Japanese economy is expected to progress in three stages.

The first stage is fluctuations in crude oil futures and exchange rates, and stock price reactions of shipping, aviation, and chemical companies. The second stage is the rise in gasoline, diesel, electricity, logistics, and airfares. The third stage is the price pass-through to food, daily necessities, building materials, agricultural materials, and manufacturing parts.

By the time households feel the impact, weeks or months may have passed since the military tensions that caused it.

Japanese Diplomacy Needs More Than Just "U.S. Support"

Japan bases its security alliance on the U.S., but stable relations with Middle Eastern countries are essential for energy. These two realities clash head-on in the Strait of Hormuz crisis.

U.S. protection of merchant ships and ensuring freedom of navigation are beneficial to Japan.

However, if blockades and fees increase military tensions and make ship operations more difficult, unconditional support is not possible.

What Japan should seek is not a binary choice between the U.S. or Iran, but securing communication routes to avoid miscalculations, mediation by third countries, clear navigation rules for civilian ships, and a verifiable framework based on international law.

Japan has maintained diplomatic relations with Iran while keeping an alliance with the U.S.

Collaborating with Gulf oil-producing countries, Oman, Europe, and the International Maritime Organization to return the safety of the strait to a multilateral framework is crucial. Both the U.S.'s "guardian" concept and Iran's "strait management" concept alone could be destabilizing factors for Japan.

Four Notable Reactions on Social Media

A review of public posts on X and forums reveals four main reactions.

However, this is not a public opinion survey, but a trend confirmed through public searches. Additionally, since post content may include unverified information and expressions based on political stances, individual claims should not be equated with facts.

The first is surprise and skepticism about the scale of the 20% burden.

Energy market commentators and geopolitical experts have reacted by saying that if converted to oil prices, it could result in an additional burden of several dollars per barrel, perceiving it as "a new tariff rather than a security fee."

There is more caution about the market psychology and insurance premiums being moved by the statement alone than the feasibility of implementation.

The second is concern about the dangers from a shipping operations perspective.

Accounts dealing with shipping and tanker information have focused on the scope of the blockade, inspection targets, ship nationalities, cargo determination, automatic identification system operation, and radio instructions that captains should follow.

The emphasis is on whether shipping companies and insurance companies will actually allow navigation, rather than the political declaration that "the strait is open."

The third is anxiety about the cost of living in Japan.

Posts in the Japanese language sphere express concerns about the impact on crude oil prices, yen depreciation, gasoline prices, electricity rates, and logistics costs.

In particular, there is a reaction that, in addition to the explanation that "there are reserves, so it's okay," one should also consider the replenishment in case of prolonged shortages, shortages of naphtha and petrochemical raw materials, and the fiscal burden of government subsidies.

The fourth is distrust of both the U.S. and Iran.

U.S. government-affiliated accounts have positioned the blockade as a limited measure against Iran, emphasizing that the passage of non-Iranian-bound ships through the strait will be protected.

In response, Iranian side and the Iranian Embassy in Japan have criticized the U.S. for breaking agreements and infringing on the sovereignty of the strait.

Among general users, a cool view is spreading that it is not about "who controls the strait," but rather that the costs of the prestige struggle between the two countries are being borne by importing countries and consumers.

There are also voices on social media supporting hardline measures.

The opinion is that clear deterrence by the U.S. military is necessary to stop Iranian ship attacks and passage obstructions. However, overall, posts questioning the legal basis of the fee proposal, accidental collisions, and the impact on insurance and logistics were more prominent than the deployment of military force itself.

Five Points Japan Must Confirm Immediately

For the Japanese government and companies, the first thing to confirm is the actual operational scope of the blockade.

The impact will vary greatly depending on whether only ships bound for Iran are targeted, whether ships transshipping Iranian crude oil in third countries are also targeted, and how long inspections take.

Next, it is necessary to determine whether the 20% burden remains a political statement or becomes a concrete system.

Even if not institutionalized, if war risk premiums, crew allowances, and charter fees rise, procurement costs for Japanese companies will increase.

Third is ensuring the safety of Japan-related ships.

In modern shipping, where ship registration, operating companies, cargo, and destinations are complexly divided, safety is not guaranteed just because it is a "Japanese ship." A system is needed where the government, shipping companies, shippers, and insurance companies share the same information and do not issue contradictory instructions to the ship's captain on site.

The fourth is not only the remaining amount of reserves but also the release speed and supply-demand by product.

Even if there is enough gasoline, shortages of aviation fuel or naphtha are possible. It is necessary to understand the impact by industry and indicate early where supply constraints may occur.

The fifth is not to end the crisis as a temporary price issue.

Diversification of crude oil procurement sources, refinery adaptability, renewable energy, nuclear power, storage batteries, energy conservation, and recycling of chemical raw materials, which may seem costly in peacetime, function as insurance in emergencies.

The Question is Not "Control of the Strait" but Management of Dependency

The U.S. resumption of the maritime blockade is both pressure on Iran and a warning to energy-importing countries.

Japan is geographically distant from the strait militarily, but economically, it is right next to it. Changes in tanker routes, rising insurance premiums, and fluctuations in oil prices reach domestic gas stations, factories, airports, and supermarkets with a time lag.

It is still uncertain whether the U.S. can restrain Iran's actions with the blockade or provoke retaliation. The 20% burden may not be realized as is.##