A Doctor Facing Terminal Cancer Reveals How He Turned ¥500,000 into ¥5 Billion Through Value Stocks

He started with 500,000 yen at age 20 while still in college and became an “Okuribito” (a person who has earned over 100 million yen through investing) at 29.

The term “Okuribito” refers to investors who have built up assets worth hundreds of millions of yen. This time, we feature Tāchan, who began developing his own value stock investing strategy as a university student and has since amassed more than 5 billion yen in stock assets. By systematizing and refining his practical approach to value investing, Tāchan reminds us that stock investing can yield profits if you take the time to carefully select your stocks.

[Profile: Tāchan]

Born in Hyōgo Prefecture in 1975. A physician who graduated from a national university’s medical school. At age 20, while still in university, he read Robert Kiyosaki’s Rich Dad Poor Dad, which sparked his interest in investing. Starting with 500,000 yen in seed money, he began investing in stocks. Through self-study, he discovered value stock investing during his student years. By focusing his own method—concentrated investments in self-selected value stocks—he became an Okuribito (an investor with over 100 million yen in assets) at age 29.

Although his funds temporarily decreased during the 2008 Lehman Shock, he did not alter his investment style and steadily grew his assets. With the tailwind of Abenomics, his net worth reached 1 billion yen by 2013. After a period of plateau, his passion for investing was reignited when he was diagnosed with rectal cancer in 2022. Through concentrated investments in shipbuilding stocks, his assets reached 5 billion yen by 2024. After four surgeries, however, metastases to his lungs and liver were discovered in 2024 at age 49. His doctor has told him, “You may make it to 50, but 51 is uncertain.”

It’s something we think we know—but do we really?
The surprisingly vague concept of value stocks.

The investor featured this time, Ta-chan, is a true master of value investing.

A value stock is essentially a bargain stock, defined as a company whose stock price is lower than its intrinsic value as measured by investment indicators. When the market eventually recognizes the true worth of such a company, its stock price is expected to rise to a fair level.

So how are value stocks discovered? In general, value investors rely on metrics such as PER (Price Earnings Ratio) and PBR (Price Book-value Ratio). Using a brokerage’s stock screening tools, they might set conditions like PER below 10 or PBR below 0.8 to extract undervalued stocks. From there, they narrow down candidates by evaluating business performance and financial health.

However, this common approach has a major flaw: it doesn’t clarify what truly makes a stock undervalued.
While it may find stocks with lower PER or PBR compared to market averages, that’s merely a relative judgment. Changes in market conditions, exchange rates, or the economy can easily erase that sense of cheapness. In the end, it may amount to nothing more than buying a low-priced stock—without understanding its real value.

In contrast, Ta-chan digs deeper into what specifically makes a company undervalued.
His unique method sharpens the definition and practice of value investing with remarkable clarity.

Investment Methods That Evolve with a Company’s True Value

Ta-chan defines a company’s value as “owned assets + future profits.”
Based on this, he created the following formula for stock prices:
Stock Price = Owned Assets + Future Profits (+ Bias).

“Bias,” he explains, “refers to investors’ prejudices—like ‘this company’s stock will definitely rise’ or ‘this company has no future.’ In theory, a company’s stock price should align with its actual value, but once these biases are added in, prices can become overvalued or undervalued. To succeed in value investing, it’s essential to remove such biases and focus purely on the company’s true value.” (Ta-chan)

Ta-chan’s value investing strategy can be divided into three types: 1. Asset Value Investing – focuses on a company’s owned assets. 2. Earnings Value Investing – emphasizes future profit potential. 3. Cyclical Value Investing – targets stocks whose prices are undervalued due to biases, even when both their assets and future profits are sound.

By classifying investments in this way, it becomes clear what exactly is undervalued and why it’s considered undervalued—resolving the ambiguity that often clouds conventional value investing.

As Ta-chan notes, the difficulty of each approach—and the potential returns—both increase in the order above.

He refers to these as his three truly profitable investment strategies.
Details on his current portfolio, his outlook on the stock market, and the stocks he’s currently watching are shared in the premium edition of FRIDAY Subscription.

■Mr. Tachan’s X (formerly Twitter) “Tachan @Bubble Old Man” is here

“I want you to use money to expand the freedom in your life and eliminate your worries about the future.” It was from this desire for his daughters that “Lessons from an Investor Father Who Turned 500,000 Yen into 5 Billion Yen” (Diamond, Inc.) was born.