Seoul, South Korea – When Kim Ha-young, a Seoul office worker in her 30s, came into a little unexpected cash last year after paying the deposit on her rented apartment, she did something she had never done before.

She bought shares.

With little knowledge of the market, Kim picked SK Hynix and Samsung Electronics, South Korea’s largest manufacturers of memory chips used for AI, on a whim.

“I mean, when you think of Korea, you think of Samsung, right?” Kim told Al Jazeera, explaining that she started investing “with no prior research at all”.

Then, in September, Kim’s shares began to climb rapidly.

At first, Kim told herself she’d be happy with a gain of 50,000 won ($33).

But as SK Hynix and Samsung Electronics’ stock price continued to soar, she continued buying and selling shares before deciding in February to hold onto her stock.

Since then, Kim’s stakes in Samsung Electronics and SK Hynix have both more than doubled in value.

“I was in the green, so I told myself to just wait it out – it had climbed nicely over the past half year,” Kim said.

Kim is among a swelling number of everyday South Koreans who have waded into the stock market for the first time during the most spectacular rally in the country’s history.

The number of South Koreans who own stocks surged from about 6 million in 2019 to more than 14.5 million at the end of 2025, according to the Korea Securities Depository.

That number has likely ballooned over the past six months, as South Korea’s benchmark Kospi has nearly doubled in value, making it by far the best-performing major index worldwide.

As of May, the number of active stock trading accounts in the country stood at 105.22 million, a rise of 6.93 million from the end of last year, according to the Korea Financial Investment Association.

The boom is a remarkable turnaround for South Korea’s stock market, which was long written off by investors as a laggard compared with its global peers.

Despite birthing household names, such as Samsung and Hyundai, South Korea was for decades infamous for the “Korea discount”, a label used to describe the usually low valuations of Korean firms.

“The same business would be valued lower here than in global markets,” Jung Jiggwang, head of corporate finance at Woori Bank, told Al Jazeera.

Market watchers have attributed the South Korean market’s poor performance to weak corporate governance under the country’s family-run chaebol system and, above all, meagre shareholder returns.

Korean firms long had a reputation for disregarding the interests of small investors, Jung said, which bred a culture of short-term trading and “unnecessary volatility”.

Like his predecessors, South Korean President Lee Jae-myung came into office pledging to shed the country’s image as an investing backwater and vanquish the “Korea discount” once and for all.

During his campaign for the presidential election last June, Lee pledged to lift the Kospi to 5,000 points, a milestone the index blasted past in January and has since far exceeded.

Once a small-time day trader who, in his telling, regularly lost money in the market, Lee’s administration has spearheaded a series of stock market reforms, including allowing minority shareholders to concentrate their votes on their preferred candidates when electing board members.

Lee has expressed his hope for more everyday citizens to invest in the market, in part to loosen Koreans’ attachment to property, the traditional store of wealth in Asia’s fourth-largest economy.

That attachment has helped create one of the least affordable property markets on the planet, with the average 84 square-metre (904sq-foot) apartment in Seoul selling for 2.14 billion won ($1.4m).

“Residential real estate has no particular productivity beyond functioning as a home,” Woori Bank’s Jung said.

“Whereas companies’ main purpose is to create new technologies or services and grow added value,” he said.

With South Korea’s economy facing the prospect of weak long-term growth amid a rapidly ageing labour force, capital needs to be steered towards “good companies with high productivity”, Jung said.

At a news conference to mark his first year in office on Monday, Lee blamed controlling shareholders for keeping retail investors away even when firms were making big profits, saying they would “go around the back, stick in a pipe, and siphon it all off.”

Simply cleaning up those “abnormalities”, Lee said, had helped boost the stock market past the 5,000-point threshold.

While the Lee administration has rolled out a series of reforms to safeguard the interests of minority shareholders and draw new investment, the market’s stellar rise has been largely driven by a chronic global shortage of memory chips.

The AI-driven demand for the chips has delivered Samsung Electronics and SK Hynix record-shattering profits, catapulting the companies into the exclusive ranks of firms with a market capitalisation of at least $1 trillion.

Long a believer in the value of Korean blue-chip stocks, Kim Do-hyun, a 30-year-old worker at an AI startup in Seoul, was convinced to finally jump into the market by the ongoing rally and bullish earnings forecasts for the year ahead.

“I just thought having money in the form of cash during this boom is a waste,” Kim told Al Jazeera.

While the market’s rise has been spectacular, it has also been volatile, raising concerns about how long the rally can last.

On Monday, the Kospi plummeted nearly 9 percent, triggering the exchange’s circuit breaker for the second time this year, following a record 12.06 percent plunge in March.

Woori Bank’s Jung said there is reason to be cautiously optimistic over the long run, noting that the rally has been concentrated in a handful of mostly tech-related firms, while hundreds of profitable companies in other sectors have been overlooked.

The biggest danger, Jung said, is that US tech giants fuelling chip demand, such as Microsoft, Apple and Amazon, rein in their spending faster than expected.

“The cause of a decline could come from the same place as the cause of the rally,” he said.

Kim Ha-young is aware of the risk of getting carried away.

After experiencing the rush of seeing big gains on paper, Kim now hopes to grow her investment slowly and steadily so she has the option to put down a deposit on a home or take care of retirement.

“I think the best thing is to invest in good companies for the long term,” she said.

“I’m trying to let go of greed and just keep at it without putting pressure on myself.”