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Choruko began investing in 2011 while still at university, using JPY2.4 million given to her by her father to buy stocks. For the next seven years, however, she barely paid attention to her investments.

That changed in 2018, when her husband left his job because of work- stress. While reviewing the family’s finances, Choruko discovered that her original investments had grown to nearly JPY16 million, Diamond Online reported. “That was when I truly felt the power of the stock market,” she later recalled in her memoir.

Pregnant with her first child and anticipating an increase in Japan’s consumption tax, Choruko began seriously studying stock charts and trading strategies.

During maternity leave in 2019, she plunged into day trading. Betting that semiconductor demand would rebound after being hit by U.S.-China trade tensions, she put her capital into Tokyo Electron shares and also used margin trading, according to Friday.

While caring for her newborn, she followed short-term price movements on her phone and executed more than 1,000 trades a month. Within six months, her portfolio had surged to JPY50 million.

By January 2021, Choruko was making around JPY500,000 a day from day trading, and her total assets surpassed JPY100 million. But her rapid success also made her overconfident. “At that time, I developed an illusion of competence, which led to my later failure,” she told Huffington Post Japan.

The setback came after Choruko shifted her attention to high-growth technology stocks. Expecting strong earnings to trigger a rally, she made a concentrated bet on AI inside Inc., whose shares had already fallen 34% from their peak.

Instead of rising after the company’s earnings announcement, the stock plunged. Choruko lost JPY24 million in a single day, and by July 2021 her assets had fallen to JPY68 million. Shaken by the loss, she temporarily stopped trading.

She later admitted that she had failed to recognize that expectations for strong earnings had already been reflected in the share price.

“I was pursuing profit without considering that. It was completely the mindset of a gambler with no logical basis,” she said.

Several weeks later, Choruko returned to the market after spotting a major company preparing to pay a dividend equivalent to about 10%. The trade helped lift her assets back to JPY88 million before she sold the position to avoid a potential decline after the dividend payout.

When her maternity leave ended, Choruko no longer had enough time for intensive day trading. She therefore changed her strategy, developing a swing-trading approach centered on buying shares in large, industry-leading companies during sharp market sell-offs and holding them for days or weeks.

The strategy helped her capitalize on periods of extreme volatility. During market turmoil surrounding the Russia-Ukraine conflict in 2022, she made JPY500,000 in a single day, according to JBpress.

Her portfolio faced another major shock in early 2026, when market turbulence erased JPY90 million from its value. Rather than retreating, Choruko bought heavily into a major manufacturing conglomerate during the sell-off. The subsequent recovery pushed her total portfolio above JPY500 million.

Choruko eventually left her job as a pharmaceutical representative to gain greater control over her time. She established public relations and real estate businesses, hired a former colleague as a remote assistant and outsourced household chores, allowing her to devote more time to investment research.