[Lesson] What Jun Mizutani’s Investing Failures Teach Us: Why Long-Term Investing Suits Ordinary People Better

Hey everyone, Hirokichi here. This time I want to use the investing failures that former Olympic table tennis champion Jun Mizutani has been openly sharing as a case study, and think together about why long-term investing suits ordinary office workers and homemakers better than short-term trading.

Nine years in, eight straight losing years, roughly ¥200 million invested

Jun Mizutani won gold in mixed doubles table tennis at the Tokyo Olympics and now works as a TV personality and investor. Appearing on the BS TV Tokyo program “Money no Manabi” (aired June 1, 2026), he called himself a “reverse okuman-chōja” (someone who should have made 100 million yen but lost instead) and said the following (source: TV Tokyo Plus):

“I love money. I trade both stocks and FX. I started back when I was still an active player, and this is my ninth year now. I’ve easily lost 100 million yen (about $650,000) on a single stock.” “Altogether, I’ve put in about 200 million yen (about $1.3 million).”

What’s even more striking is that in nine years, he has never once finished a year in the black — eight years in a row have ended in the red. About half of his money sits in FX trading, and he admits, “The moment I make even a little profit, I reinvest that exact amount, and then everything collapses on me.”

His annual loss in 2024 was, in his words, “enough to buy a house in Tokyo” (source: Sanyo Shimbun Digital). In 2025, appearing on the YouTube channel “Shin R25,” he said, “If I hadn’t invested this year, I could have bought the top-of-the-line Lexus LS. Right now I’m down roughly a house plus that LS.”

Ten free minutes, fifteen million yen gone: the cost of “just kind of” investing

One episode from the show says it all. One afternoon, after wrapping up work, Mizutani had ten spare minutes while waiting for his manager. He noticed a stock that had jumped about 10% that day and, on nothing more than the casual guess “this will probably go up again tomorrow,” placed a ¥100 million (about $650,000) buy order. The very next day, the stock crashed almost to its daily limit-down, and ¥15 million evaporated in a single day (source: TV Tokyo Plus).

On June 15, 2026, he posted on X (formerly Twitter) that he had already sold three stocks — Kioxia, Furukawa Electric, and SoftBank Group — writing, “Obviously I don’t hold these anymore, I cut my losses after they crashed the day I bought them.” All three stocks then surged on the very day of that post, which became a talking point online (source: livedoor News). He has also previously posted a screenshot showing a settled loss of ¥10,375,669 (about $67,000).

Show host Pack commented that “investing on a whim is dangerous,” and professional investor DUKE. said, “Buying without a real reason means you’re already losing before you even start.” The program also revealed that Mizutani checks stock prices on his phone constantly — backstage, in taxis, during meals — and that his manager has to think carefully about when to talk to him.

“Sell, then watch it soar” isn’t just Mizutani’s bad luck

Selling at a loss right before the price jumps back up. Many investors chalk this up to their own bad luck, but behavioral economics offers a decent explanation.

Mizutani’s comment, that he reinvests any profit the moment he makes it until everything collapses, sounds close to the “house money effect,” where a person treats gains as if they were never really their own money and takes on bigger risks than usual as a result. On top of that, when a stock is dropping sharply, investors whose psychological pain reaches its limit tend to sell all at once (a pattern described by prospect theory as loss-aversion bias), and that selling pressure often finishes right around what turns out to be the bottom.

In other words, short-term trading built on “buy on a whim, cut losses on a whim” leaves your timing at the mercy of your own emotions. In my view, consistently getting that timing right, something even professional investors struggle with, through casual short-term trades takes a level of nerve and experience that most people simply don’t have.

Why long-term investing suits ordinary people better

Mizutani can keep investing through huge losses because of his fame and income, but for most office workers and homemakers, copying that style is far too risky. Here are three reasons I think long-term investing is the better fit for ordinary people.

(1) You can build a system that isn’t at the mercy of your emotions. With something like Japan’s new NISA installment investment framework, where a fixed amount is automatically invested every month, you cut out the risk of trading “on a whim” every time the market moves.

(2) The longer your time horizon, the narrower the swing in returns. According to data published by Japan’s Financial Services Agency (FSA), when investing steadily in a diversified mix of domestic and international stocks and bonds, a 5-year holding period produced annual returns ranging from about -8% to +14%, while a 20-year holding period narrowed that range to roughly 2% to 8% (source: Financial Services Agency).

As the chart shows, the longer you hold, the narrower the range of returns gets, and the lower the risk of ending up below your original investment. With short-term trading, a single ten-minute decision can swing your whole portfolio, but with long-term investing, there’s no need to react to the market’s daily ups and downs in the first place.

(3) You can focus on your job and your life without being glued to the market. Mizutani once said, in the middle of an interview, “In the ten minutes we’ve been talking, I’ve lost 3 million yen (about $20,000)” — that kind of lifestyle just isn’t realistic for most people. With long-term investing, once you set up the system, you can largely leave it alone.

It’s worth noting that GPIF (the Government Pension Investment Fund), one of the largest pension funds in the world, also takes a long-term, diversified approach across domestic and international stocks and bonds rather than chasing short-term price moves. If you’re curious, check out my earlier article, How Has GPIF’s Investing Changed Since the Abe Era? From the 2014 Overhaul to the 2026 “Return to Domestic Assets” Debate.

Points worth keeping in mind going forward

Looking at what we can take from Mizutani’s story, I’d sum up three points that ordinary people should keep in mind when investing.

(1) Stop “buying on a whim, selling on a whim” — decide your buy criteria and sell criteria in advance.
(2) Instead of chasing short-term price moves every day, build an installment-investing system and keep some distance from the market.
(3) Understand psychological quirks that everyone has, like loss-aversion bias and the house money effect.

Mizutani’s posts get attention mostly for the sheer size of the losses, but I think there’s real value in the way he shares his failures so openly. What ordinary people should copy isn’t his style, it’s the lesson underneath it: when you let emotion drive your decisions, you tend to repeat the same mistakes.

Let’s keep at it, slow and steady. See you next time!

日本語版はこちら → 【教訓】水谷隼さんの投資失敗から学ぶ、一般人こそ「長期投資」を選ぶべき理由

* This article is for informational purposes only and does not recommend any specific investment. Please make investment decisions at your own responsibility.

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