In the third week of September 2026, the Korean stock market had one of its worst weeks of the year. The KOSPI fell more than 3 percent. The won slid from 1,345 to 1,389 against the dollar. Meanwhile, in the same five trading days, Korean individuals wired $1.12 billion into American shares. They did not buy Samsung or Hyundai. Instead, they bought a triple-leveraged semiconductor fund listed in New York. That single week explains why Korea US stock investors have become one of the most watched pools of retail money in the world.

Koreans have a nickname for them: seohak gaemi, or “western-study ants.” The term is a pun. During the pandemic, retail traders who piled into the KOSPI were called donghak gaemi, after a 19th-century peasant uprising. Consequently, the ones who crossed the Pacific became the western branch of the same colony. Ants, because they are small and numerous. Western, because their money now lives on the Nasdaq.

Four years ago, that colony held about $44 billion in US equities. Today it holds roughly $190 billion, and it briefly crossed $200 billion in May. For foreign investors, the story matters for reasons that go well beyond a curiosity about Tesla fandom. It moves the won. It shapes the earnings of every Korean brokerage. Above all, it is the clearest evidence that ordinary Koreans still do not trust their own market, even in a year when that market set records.

Korea US Stock Investors: From $44 Billion to $200 Billion

The numbers come from the Korea Securities Depository, which tracks every foreign share that Korea US stock investors hold through a domestic brokerage. At the end of 2022, Korean individuals and institutions held $44.2 billion in US stocks. A year later, the figure was $68.0 billion. By the end of 2024, it had reached $112.1 billion. Then, at the close of 2025, it stood at $163.6 billion, according to Kyunghyang Shinmun.

The pace did not slow in 2026. By January 15, holdings had crossed $170.5 billion, or about 251 trillion won. A sharp correction in March pulled the total down to $146.5 billion. However, two months later the recovery was complete. On May 14, Korean holdings of American shares passed $200.01 billion, a figure Seoul Economic Daily translated as 300 trillion won. That is more than 37 percent above the March low, achieved in roughly eight weeks.

In other words, the pile grew 4.5 times in four years. Part of that is price. Tesla, Nvidia and Palantir all rose enormously over the period, so existing positions inflated on their own. Yet a large share is fresh money. In January 2026 alone, net purchases of US stocks reached $5.0 billion, more than double the December figure, Reuters reported. By mid-September the custody total sat at $189.9 billion, up 10.7 percent from late July.

For scale, consider that Korea’s entire domestic equity market was worth roughly 3,000 trillion won at its 2026 peak. Korean retail investors US stocks holdings are therefore equivalent to about a tenth of the home market. No other major economy has a retail base that keeps this large a share of its wealth in a single foreign country’s stocks.

What Korean Retail Investors in US Stocks Actually Buy

The portfolio of Korea US stock investors is not diversified, and nobody pretends otherwise. As of January 2026, the largest single holding was Tesla at $27.6 billion. Nvidia followed at $17.9 billion. Then came Alphabet at $7.2 billion, Palantir at $6.5 billion, Apple at $4.3 billion and Microsoft at $3.3 billion.

Notice what is missing. There is no Berkshire Hathaway, no Johnson & Johnson, no broad-market dividend fund near the top. Instead, the list reads like a concentrated bet on American artificial intelligence and one very famous CEO. Tesla alone accounts for more than one dollar in every seven that Koreans hold across the entire US market.

The ETF holdings tell an even stranger story. The Invesco QQQ Trust, which tracks the Nasdaq-100, sits at $3.9 billion. Vanguard’s S&P 500 fund is close behind at $3.7 billion. Right next to them, however, is ProShares UltraPro QQQ, better known as TQQQ, at $3.4 billion. That fund delivers three times the daily move of the Nasdaq-100. It is designed for day traders. In Korea, it functions as a core holding.

The leverage habit

Americans rarely hold triple-leveraged funds for long, because daily rebalancing erodes returns in choppy markets. Korean individuals, by contrast, treat them as a way to make a smaller stake work harder. As a result, Direxion’s SOXL, which triples the daily return of a semiconductor index, has become the single most traded American product among Korean retail accounts.

The pattern repeats every time chips fall. In the last week of July 2026, the Philadelphia Semiconductor Index dropped 8.4 percent. During those same eight days, Korean investors bought $1.05 billion of SOXL, Herald Business reported. Then, in early September, they sold $677 million of it as the index recovered. A week later they bought it back. This is not passive investing. Rather, it is a national habit of buying the dip with borrowed exposure.

Anyone who has followed the Korean stock market rally and crash of 2026 will recognise the temperament. The same risk appetite that pushed the KOSPI from 2,800 to 8,000 now operates in New York, only with more leverage.

September 2026: Four Days, $1.5 Trillion Won

The most revealing episode of the year arrived in mid-September, because it ran two markets side by side.

From September 1 to 11, seohak gaemi were net sellers. They unloaded $131 million in US shares. In particular, they dumped SOXL and moved money into SGOV, a short-term Treasury fund, which looked like a retreat into safety. The won had strengthened below 1,400, so the timing made sense.

Then the semiconductor rally resumed. Between September 14 and 18, Korean individuals bought a net $1.118 billion, roughly 1.55 trillion won, according to Maeil Shinmun. SOXL took $457 million of it. Nvidia received $46 million, Micron $36 million, IonQ $27 million, SanDisk $26 million and TSMC $24 million. The month flipped from net selling to net buying in four sessions.

Meanwhile, the home market went the other way. The KOSPI dropped 3.14 percent that week. By contrast, the Nasdaq-100 gained 1.28 percent, and the Philadelphia Semiconductor Index jumped 7.1 percent. Korean chipmakers fell while American chipmakers rose, and Korean money followed the rise.

For a foreigner, the lesson is simple. Korea US stock investors do not wait for a calm market. On the contrary, they move fastest when volatility is highest, and they move in one direction: toward whatever American sector is running.

Buying Samsung Through New York

Here is the twist about Korea US stock investors that catches most outsiders off guard. In May 2026, one of the most popular purchases among Korean individuals was the Roundhill Memory ETF, ticker DRAM. That fund holds Micron, SanDisk, Samsung Electronics and SK hynix, with the two Korean names making up roughly half the portfolio, as The Motley Fool describes.

Read that again. Koreans were buying Samsung and SK hynix, the two largest companies on their own exchange, through a dollar-denominated fund listed in the United States. They could have bought the same shares in Seoul with no currency conversion and no capital gains tax. Nevertheless, they chose New York.

Several explanations exist. Some investors wanted dollar exposure at a time when the won looked fragile. Others liked bundling Korean memory makers with Micron in one ticker. Still others simply trust the American wrapper more than the Korean listing. Whatever the reason, the choice says something uncomfortable about how Koreans view their home exchange. The memory chip supercycle was made in Korea, yet many Korean investors preferred to own it from abroad.

The same month, Intel drew more than $640 million in net purchases. That is a turnaround bet on a struggling American company, made by people who could have bought a booming Korean one instead.

The 22 Percent Tax Korea US Stock Investors Pay Anyway

The tax code should push Korea US stock investors in the opposite direction. Nonetheless, it has failed to do so.

Profits on foreign stocks are taxed at 22 percent, including local surtax, after an annual deduction of 2.5 million won, or roughly $1,800. Gains on Korean listed shares, by contrast, are completely untaxed for anyone below the large-shareholder threshold. On paper, the domestic market wins by a wide margin. Every dollar of Tesla profit costs a Korean investor 22 cents that the same profit on Samsung would not.

Yet Korean overseas stock investing kept growing through every version of that rule. The tax is an annual settlement, filed each May, and most investors treat it as a cost of admission rather than a deterrent. In fact, brokerages now compete on tax-loss harvesting tools and automated filing, which has turned a supposed barrier into a service business.

In 2026, the government tried a carrot instead of a stick. The RIA account, whose acronym stands for “return to domestic investment,” lets investors sell foreign stocks, bring the proceeds home and receive an income deduction on the gains. The deduction was 100 percent for sales in the first quarter, 80 percent in the second and 50 percent for the rest of the year. Conditions apply, however. Only shares held before December 23, 2025 qualify, sales are capped at 50 million won per person, and the money must stay in Korean equities or cash for at least a year, according to Toss Bank’s guide.

The result was modest. April 2026 did bring the first month of net selling in ten months, at $469 million. Even so, that outflow reversed by May, and holdings hit their record two weeks later. A one-year, 50-million-won incentive was never going to move a $200 billion position.

Why Korean Overseas Stock Investing Beats the KOSPI

Ask one of these Korea US stock investors why they left, and the answers rarely involve returns. The KOSPI, after all, produced the hottest rally in the world in early 2026. Instead, the complaints are structural. Together they describe what professionals call the Korea Discount, only in the language of individuals rather than fund managers.

Dividends. Korean companies historically paid out a far smaller share of profits than American ones. An investor who wants income from stocks has few domestic options, whereas the S&P 500 offers hundreds.

Governance. Controlling families run most large Korean groups through small direct stakes and circular holdings. Minority shareholders have limited protection when a chairman decides to merge two affiliates at an unfavourable ratio. For an outsider’s view of how those structures work, the ownership map of Samsung is a useful place to start.

Information. American companies host quarterly calls, publish detailed guidance and answer analyst questions in English. Many Korean mid-caps do none of that. Retail investors who learned to read a 10-K on Reddit find Korean disclosure thin by comparison.

Trading hours and access. A Korean office worker can trade Nasdaq at night after work. Domestic trading ends at 3:30 in the afternoon, when most people are still at their desks. Fintech apps, particularly Toss and its rivals, made the overnight American session as easy as the daytime Korean one.

Currency. For years, a weak won made dollar assets look like a hedge. Someone who bought Nvidia in 2023 gained on the stock and on the exchange rate at the same time. That logic wobbled in 2026 as the won recovered, yet the habit remained.

None of these points is new. What changed is that individuals now act on them at scale. The Korea Discount used to be a phrase from foreign fund reports. Now it is a household decision.

The Government’s Counteroffer

Seoul has noticed, and it has tried nearly everything short of capital controls.

The Corporate Value-up Program, launched in 2024, pushes listed companies to publish plans for raising shareholder returns, as Glass Lewis explains. Commercial code amendments now require directors to act in the interest of all shareholders, not only the company. Dividend taxation was eased. Furthermore, the RIA account described above offered a direct, if temporary, bribe to come home.

There is also a currency angle. By February 2026, the won was trading near 17-year lows around 1,450, and the Bank of Korea openly admitted that domestic dollar demand, not foreign speculation, was driving the weakness. Residents’ dollar deposits had hit a record $119 billion. Officials asked exporters to convert earnings into won and nudged the National Pension Service to sell dollars. In short, the central bank was fighting its own citizens’ brokerage apps.

Each measure has had some effect on Korean overseas stock investing. The KOSPI’s record run owed part of its strength to governance reform, and dividend payouts have risen. Nevertheless, the custody data suggests that Korea US stock investors treat these changes as a reason to own both markets rather than to abandon the American one. Money came home in April. It went back out in May. The pattern has repeated all year.

The deeper problem is that the reforms address governance, whereas the exodus is also about product. Korea has no Nvidia. It has world-class memory makers and one enormous conglomerate, and both already sit in most domestic portfolios. A retail investor who wants exposure to AI software, electric vehicles or quantum computing must look abroad, regardless of how well Korean boards behave.

What Korea US Stock Investors Mean for the Won, Brokers and Foreign Investors

Foreign readers may wonder why a domestic retail habit deserves attention. Three effects make Korea US stock investors relevant far beyond Seoul.

The won

Every dollar of net buying is a dollar of won sold. When Korean individuals bought $5 billion of US stocks in a single month, they became one of the largest sources of dollar demand in the economy. Consequently, the won now has a retail-driven floor under its weakness. Anyone trading the currency, or holding Korean bonds, has to watch the Securities Depository’s weekly data alongside the trade balance. A surge in SOXL purchases can push the won down as surely as an oil price spike.

The brokerages

Korean securities firms once earned most of their commission income from domestic trading. Today, overseas brokerage is the growth engine. Foreign stock commissions are higher, currency conversion adds a spread, and margin lending on US positions is a new business line. The internet-only banks and fintech apps that captured young investors have built entire product lines around American shares. For an investor in Korean financial stocks, the direction of the seohak gaemi is a direct earnings driver.

The KOSPI itself

Finally, the outflow acts as a ceiling on domestic valuations. Foreign institutions have long been the swing factor in Korean equities. Increasingly, however, the domestic retail base is a second swing factor, and it can leave. A market whose own citizens keep 300 trillion won abroad will always struggle to close the valuation gap with peers, no matter how many governance reforms pass.

A Practical Note for Foreigners Who Want to Join Korea US Stock Investors

If you live in Korea and hold a resident registration card, you can open the same brokerage accounts that Korea US stock investors use and buy American shares through them. The apps are excellent, the fees are competitive, and overnight trading covers the full US session.

Several things are worth knowing first. The 22 percent capital gains tax applies to residents regardless of nationality, and it is self-reported each May. Dividends are withheld at source in the United States and then reconciled in Korea. Most apps still operate mainly in Korean, although Toss, KakaoPay Securities and a few others offer partial English interfaces. Finally, your home country may tax the same gains, so check whether a treaty applies before you copy the local enthusiasm for leveraged ETFs.

The Ants Are Not Coming Home

The Korean government has spent two years building reasons for its citizens to invest at home. The market obliged with a historic rally. Yet the custody numbers barely flinched. Korean holdings of American stocks dipped in March, recovered by May and were rising again in September, while the KOSPI fell.

That persistence is the real story. Korea US stock investors are not chasing a single stock or a single year. Rather, they have concluded that the American market offers something the Korean one does not, and that conclusion has survived a tax penalty, a currency reversal and a domestic bull run. Until the Korean market can offer the same combination of governance, product and access, the western-study ants will keep marching, one leveraged ETF at a time.

Seoulz covers the money flows reshaping Korea, from the KOSPI’s 2026 crash to the won-backed stablecoin race.