Should People in Their 20s Prioritize Self-Investment Over Stocks? The Conclusion Found by Comparing 3 Types of Investments by Return Rate [AI Investment Lab #12]

When you think about starting to invest, the first things that come to mind are probably stocks or investment trusts.

But in reality, I believe there are three main types of "investment".

And for you in your 20s, the one with the highest return rate...
might not be stocks.

Here is the conclusion first: the investment with the highest return for those in their 20s is "self-investment."

Investing in skills like English or certifications can, according to data, pay for itself in the first year and continue to provide returns every year. The return rate can be orders of magnitude higher than the expected return of stocks (5-7% per year).

In this article, we will verify the basis for this using "specific monetary amounts."

I am an engineer who entered the IT industry as a new graduate with no experience, earned all AWS certifications in about a year, and started job hunting this spring.

I am not particularly brilliant. There are many people in the world who are more talented than I am.

Even so, I have built up my efforts through sheer volume of action and consistency.

That is precisely why, among the three types of investments, I feel that I have invested the most money and time into "self-investment."

This article is written for company employees in their late 20s to early 30s with an annual income of around 4 to 5.5 million yen who are about to start investing.

What you will learn in this article

• The 3 categories of investment: Corporate investment, real estate investment, and self-investment

• How much did a monthly investment of 100,000 yen for 10 years in stocks amount to?

• What happens in 5 years to a 30 million yen property that can be bought with an annual income of 5 million yen?

• Confirming the "annual income increase" from English and certifications using data

• Priorities by age group as asked to 3 AI companies (Claude, ChatGPT, Gemini)

1. There are 3 main types of investment

① Corporate investment (Financial investment) Stocks, investment trusts, ETFs, foreign currency, and REITs. Their value fluctuates based on corporate performance, the economy, and global affairs.

② Real estate investment Apartment management, detached house rentals, parking lots, and land. This is an investment where you rent out properties to earn rental income.

3. Self-Investment Reading, English, certifications, AI/programming, and health. These are investments that lead to future income.

You might think, "3 isn't really an investment, is it?" but...

However, I believe the structure of investing money and time to recover a return is exactly the same. In fact, when you compare them using numbers, the destructive power of 3 becomes clear.

Note that the returns of these three have different characteristics (stocks = yield, real estate = yield + asset value, self-investment = increased annual income). In this article, I will compare them using a single metric: "how effectively the money and time invested contribute to future asset formation." Please read this not as a strict side-by-side comparison, but as a map for choosing your first move.

2. Corporate Investment: 100,000 yen per month for 10 years, how much did it become? [Assuming New NISA]

First, let's start with the classic stock accumulation. What if you invested 100,000 yen every month into an investment trust for 10 years?

The principal is 12 million yen. Past 10-year performance (approximate in yen terms) is said to be about 13-15% per year for the S&P 500 and about 10-12% per year for the All Country World Index (eMAXIS Slim All Country).

When calculated, it looks like this.

For the S&P 500, it's about 24.66 million yen. That's double the principal.

However, there are two things to note.

First, there is a possibility that the past 10 years were "too good." It was a special 10-year period where the AI market and historical yen depreciation overlapped. Goldman Sachs predicts the S&P 500 will be around 6.5% per year for the next 10 years. That is why I have also included a conservative scenario (about 16.67 million yen).

Second, 100,000 yen per month is a heavy amount for this income bracket.
If it's 30,000 yen per month, please read the result as about 30% of the above.

Even so, with the New NISA, profits are tax-free. All you need to do is "open an account and set up automatic accumulation."

💡 If you are going to practice this, it is based on the premise of using an online brokerage with a large number of investment trusts and low fees. I use Matsui Securities as a sub-account, and I feel that the point return just for holding investment trusts is compatible with long-term accumulation.

3. Real Estate Investment: What if you buy a 30 million yen property with an annual income of 5 million yen?

Next is real estate. With an annual income of 5 million yen, based on loan guidelines, you can buy a property for around 30 million yen.

With this budget, good locations in urban areas are difficult, so realistically, regional condominium units or older buildings are candidates. The gross yield in regional areas is generally in the 7-10% range. Let's assume you were able to buy a property with a gross yield of 8% (annual rent of 2.4 million yen).

However, this is where the real challenge begins.

After management fees, repairs, and taxes, the actual return is 5-6%. Once you subtract loan repayments from that, what remains in your pocket is a few thousand to a few tens of thousands of yen per month. If a unit stays vacant for a few months, you're in the red.

Moreover, while property prices in urban areas continue to rise, the reality is that older properties in rural areas are difficult to sell, making it hard to benefit from price appreciation.

In short, real estate is an investment that is less about making a large profit and more about "building assets over time using other people's capital." It requires studying "business management"—specifically property appraisal, vacancy management, and repairs—which makes it a high hurdle for a beginner's first move.

I will summarize everything up to this point in one slide.

Now, what about the third option, "self-investment"?

4. Self-Investment: Actually the Best Recovery Rate

Self-investment is often overlooked because its "price doesn't fluctuate." However, when you look at the numbers, the perspective changes.

English: According to a survey by Nikkei Career, the difference in annual income between those with a TOEIC score of 499 or less and those with 900 or more is 940,000 yen in your 20s and 2.44 million yen in your 30s.

Suppose you spend 500,000 yen on a school and study materials, and your annual income increases by 500,000 yen.

Investment of 500,000 yen → Annual return of 500,000 yen.

You break even in one year, and after that, you continue to receive 500,000 yen every year. In stock terms, that's a "100% yield that continues."

AI, Programming, and Certifications: The structure is the same.

I hold 12 AWS certifications, but when I was studying for them, I saw comments many times saying, "Certifications aren't valued in practical work." Honestly, there were days when I wavered.

But I have never regretted it once.

That is because what held value wasn't the certification itself, but the ability to explain in my own words "why I got it," "what I became capable of doing," and "why that is valuable to the other party".

Any certification that allows you to explain those things will undoubtedly become market value. In my case, I was able to recover the investment in the form of a salary increase through a job change. I will write an article about this as a career piece in the near future.

Others: Job hunting itself (the best way to know your own market value), sales and communication, and health. Health is often overlooked, but if you break your body, the foundation for all other investments collapses. It is a top-priority defensive self-investment.

Reading: The cheapest self-investment. For 1,500 yen per book, you gain decades of knowledge from those who came before you. For an introduction to investing, "Winning the Loser's Game" is a classic. The foundation of the accumulation part of this article—"don't try to beat the market, just accept the market's total return"—is packed into this one book.

Why is self-investment ranked #1 only for those in their 20s?

There are three reasons.

1. You have over 40 years of working life remaining: If an annual income increase of 500,000 yen continues for 40 years, that's +20 million yen. The younger you are, the greater the total return by orders of magnitude.

2. Maximum potential for annual income growth: If you are in the 4 million yen annual income range, a 1.5 to 2-fold increase is a realistic target depending on your skills.

3. Compound interest applies to 'income' rather than 'money': While your principal is small, increasing your ability to contribute funds is faster than trying to increase your yield.

However, there are weaknesses. Returns are not guaranteed, and results require action. If you end up just 'satisfied with attending a seminar,' your recovery rate is zero.

5. Conclusion: The recommended approach for investment beginners in their 20s is the dual-wielding of 'Self-Investment x Stock Accumulation'

Let's compare the three.

The conclusion is simple.

Increase your contribution capacity (annual income) through self-investment, and put the increased income into stock accumulation.

If your annual income increases by 500,000 yen, you create an extra 40,000 yen per month for accumulation. If you invest that at 6.5% annually for 10 years, it becomes approximately 6.6 million yen.

The return on self-investment becomes the principal for corporate investment.
This connection is a strategy that only those in their 20s can execute. Real estate is a sufficient third option once your capital and knowledge have grown.

6. [Lab Tradition] When we asked 3 AI companies, they returned almost the same table

I put this conclusion to the AI as well. I asked Claude, ChatGPT, and Gemini the same prompt (July 2026): 'Prioritize these three investments by age group.'

Highlight #1: All 3 companies completely agreed that 'Self-investment is #1 for those in their 20s.'
The reasons were also almost identical, with the consensus being that 'the potential for income growth is your greatest asset.'

To be honest, I didn't expect them to be this aligned. I had predicted that at least one company would rank stocks first, so I was a bit surprised as the author that all three companies spoke in unison, saying, 'Invest in yourself first.'

Highlight #2: The only point where the 9-cell table diverged was the #2 spot for those in their 30s. ChatGPT and Claude chose self-investment, while only Gemini chose real estate. Since Gemini also gave an extreme prediction last time (#11), it seems Gemini has a 'habit of highly valuing physical assets'.

Highlight #3: The biggest discrepancy between me and the AI is 'real estate in your 20s.' I place it 2nd (the reason is in my thoughts below), but all three AIs place it 3rd. AI advice has a tendency to 'lean toward low-risk, standard moves.' It's worth remembering this.

By the way, in the previous probability forecast, the opinions of the three companies were split.AI opinions split when you 'make them bet with numbers,' but qualitative rankings converge. This is also a pattern that has become visible as I continue the verification.

Things you can do starting today

1. Corporate Investment: Open a new NISA account at an online brokerage and set up an automatic monthly investment of at least 10,000 yen

2. Self-Investment: Decide on one skill to increase your annual income (English, AI, certifications). Start with one book

3. Real Estate: Deciding 'not to buy' right now is also a sound judgment. Learning about it is free

Continue reading (How to navigate this lab)

AI Investment Lab is a series that follows the rule of 'Verification > Atmosphere,' recording AI predictions as probabilities and checking the answers later.

▶ Popular Article: #11 Is 'Switching' New NISA Wise? — The story of how the predictions of 3 AI companies were split right down the middle on one point

▶ Follow the series: If you don't want to miss the answer checks (2027/2029), go to the magazine [AI Investment Lab]

▶ Go deeper: In the paid version [AI Investment Lab Premium] (450 yen/month), I show star ratings for individual stocks and even the judgment criteria for 'why I see it that way'

▶ For engineers: For IT professionals who want to start the 'self-investment' from this article today, here is the series I use every day!!

Author's thoughts: My priority is 'Self-Investment → Real Estate → Corporate Investment'

Finally, moving away from the data, here is my personal conclusion.From here on, this is not a verification result, but 100% my subjective opinion.

1st place is, without hesitation, self-investment. It is difficult to compete with outstanding talent. However, what you accumulate daily will not betray you. If you are just vaguely looking at your own market value, or dissolving your time in alcohol, it is better to spend that hour on learning. I truly believe that. (Coming from someone who loves to drink...💦)

It might be surprising, but 2nd place is real estate. I am daring to place it 2nd, an option that all three AIs placed 3rd. Please listen to this not as data or a standard move, but entirely as my market outlook.

The greatest capital in real estate is the 'remaining years on the loan,' and this is longer the younger you are. Your 20s are the only decade where you can use 'time itself' as a weapon. In fact, the homeownership rate for 20-somethings (households of two or more) is at a record high of 35.2%, and there is a trend among the younger generation to view 'housing = assets'.

Besides, I also believe in the feeling that living in a good house tightens your resolve and changes your behavior. It's the same logic as comedians living in expensive houses to push themselves. Of course, the risks of vacancies and liquidity do not disappear, so I won't call it a 'guaranteed win.' However, there is value in taking on the challenge while you are young and sharing the process, and I hope to come across a good property myself soon. When that happens, I will show you everything in this lab.

And while corporate investment is in 3rd place, it is a 'lifelong asset'.
It has the lowest barrier to entry, can be started today, and requires almost zero effort. Financial knowledge is knowledge that compounds, becoming more effective the longer you live. Even if it is 3rd in priority, there is no option not to do it.

In short,

In your 20s, bet on yourself; in your 30s, bet on time; and throughout your life, bet on money.

This is my answer.

A word for today

I wrote this article today after finishing work as well.

It only takes 5 minutes to ask an AI.
However, it took me 3 hours to research the systems and data myself, send the same questions to three companies to compare them, and finally write down 'my own opinion, which differs from the AI'.

While writing, I asked myself many times, 'Is self-investment really number one?'
The reason I couldn't stop writing is that I believe writing this article itself is a form of self-investment for me.

If you could go back to your 20s, which one would you put your money into first?
Please let me know in the comments if you'd like.

※This article represents the author's personal views and a summary of publicly available information; it does not recommend the purchase of any specific financial products, real estate, or services. Investments carry risks, including the loss of principal, and final decisions should be made at your own responsibility. Simulations are estimates based on past performance and do not guarantee future results. The data provided is based on information available at the time of writing (July 2026). This article contains affiliate links.

X:https://x.com/home