Knowledge Memo | [Mahjong] | Why has it been loved around the world for over 100 years? The truth behind the 'brain game that teaches you about life' that is more than just gambling!

"Riichi!"
Even those who don't know Mahjong have likely heard this word at least once.
However, I think few people know that this concept of "Riichi" is a unique rule born in Japan that does not exist in Chinese or American Mahjong.

Japanese Mahjong is not just a game passed down from China; it has evolved uniquely by incorporating values and gameplay specific to the Japanese people.
Today, its value goes beyond the single word "gambling," as it has become a professional sport with the birth of the "M.League," a subject for AI research, and even a tool for health promotion among the elderly.

In this article, rather than explaining the rules of Mahjong in detail, I will delve into why Mahjong is such a "profound" game and "what kind of hints it can give us for our lives and work."

Chapter 1: Why "Riichi!" was born in Japan and underwent its own unique evolution

Tracing the origins of Mahjong leads us to mid-19th century China.
It is said that the current prototype of Mahjong was born between the late 19th and early 20th centuries through the fusion of the long-played card game "Ma Diao" and "Bone Tiles" (Ku Pai) made of ivory or ox bone.

This Chinese-born game was introduced to Japan between the end of the Meiji era and the Taisho era.
Initially, it was a pastime for intellectuals and the upper class, but by the end of the Taisho era, it was introduced in magazines and newspapers, and with the appearance of rental-table Mahjong parlors in Ginza, Tokyo, it quickly spread to the general public.
In the early Showa era, it became such a huge boom that there were over 1,500 Mahjong parlors in Tokyo alone, and after a hiatus due to the war, the second Mahjong boom arrived in 1969 with the hit of Tetsuya Asada's "Mahjong Hourouki" (Mahjong Wanderer).

And it was during this second boom that a major turning point occurred that would define Japanese Mahjong.
The Chinese rules were revised into something uniquely Japanese, with three major changes added: the "prohibition of winning on a discarded tile after declaring tenpai (furiten)," "responsibility payment for the player who dealt the winning tile," and "Riichi."

There are several theories about how Riichi was born.
One theory is that the rules played among officers of the Kwantung Army stationed in Manchuria (Northeast China) were brought to Japan by post-war repatriates.
Another theory is that the rules used among the post-war occupation forces became established. In truth, there is still no consensus on which is correct.

However, the person who systematized it as a complete set of rules is clear.
It is Mr. Daizo Amano of the Japan Mahjong Federation.
In the autumn of 1949, Mr. Amano was a regular customer at a Mahjong parlor near Sugamo Station in Tokyo.
One day, he was consulted by the parlor owner: "I want you to think of a new yaku (winning hand) to increase customers."
It is said that the moment a customer who had reached tenpai shouted, "If I discard a weird tile, I'll win!" and placed the discarded tile sideways, a flash of inspiration struck Amano.

"Declare tenpai, and do not change your hand thereafter. In return, add one yaku (fan) to your score when you win."

This is the prototype of the mid-game Riichi.
In 1952, Amano codified these rules in the Hochi Shimbun (now Sports Hochi) and spread them to the world as the "Hochi Rules."
This is the direct root of the "Riichi Mahjong" we play today.

Born from this rule reform were Japanese-unique elements such as Dora, Ippatsu, and Ura-dora.
Dora is said to be named after the fact that the three dragon tiles were called "Dragons" in Western Mahjong, and among them, the Red Dora is said to have been devised by an Osaka tile manufacturer to commemorate the 1964 Tokyo Olympics.
Ippatsu and Ura-dora were developed to add gambling elements and thrills to the "declare and wait" style of Riichi.

Why did the Japanese like this gameplay so much?
Although Chinese Mahjong has many yaku, it has a simple design where the score is determined in advance at the moment of winning, without concepts like Riichi, Dora, or Furiten.
On the other hand, Japanese Mahjong incorporated the tension of "daring to declare Riichi and wait even when you can win immediately," and the element of "luck-based upside" known as Ura-dora, giving the game a narrative and drama.
This may have something in common with the Japanese sensibility that values the aesthetics of the process, not just the results.

Chapter 2: Why has Mahjong been loved for over 100 years?

The reasons why Mahjong remains timeless despite its history of over 100 years can be summarized into three main points.

The first is that "the development is completely different every time."
Mahjong uses 136 tiles, and because elements such as the initial hand, self-draws, other players' discards, and calls are intertwined, the same situation never occurs twice.
Unlike games like Shogi or Go where the entire board is visible, you are forced to make completely different decisions each time amidst invisible information.
This sense of "once-in-a-lifetime encounter" is the biggest reason why you never get bored.

The second is that "there is a possibility that even a beginner can beat a pro."
Because there is plenty of room for coincidence to occur within a single game, it is possible for someone who has just started Mahjong to defeat a top pro, at least for that day and at that table.
This "possibility of an upset" is a charm unique to Mahjong that is not often seen in pure skill games like Go or Shogi.
That is why the expectation that "I have a chance too" draws many people to the table.

The third is the "profoundness that never ends even if you study for a lifetime."
The "technique for winning quickly," known as tile efficiency, is so deep that it cannot be fully researched, and on top of that, there are layers of pushing and folding based on the score situation, techniques for reading the opponent's psychology, and the sense of reading the flow of the table.
The bottomlessness of the competition of Mahjong lies in the fact that even after playing for decades, you never see a point of arrival where you can say, "This is complete."

Chapter 3: Even though Mahjong is a "luck game," why do skill differences emerge?

Mahjong is sometimes ridiculed as a "luck game."
In fact, if you look at only one game or one night of play, the element of luck acts very significantly.
It is not uncommon for a strong pro to lose to a beginner.
However, as you repeat the number of games into the hundreds or thousands, a clear difference in skill emerges.
This is one of the most important points in understanding the competition of Mahjong.

The key to understanding this phenomenon is the concept of "expected value."
Expected value is an indicator that shows how much profit (or loss) can be expected on average in the long term when a certain choice is made.
For example, when hesitating whether to declare Riichi in a game in front of you, a pro thinks not only about "whether I can win this game" but also from the perspective of "how much will I gain on average if I repeat this decision 100 times?"
Luck is involved in the results of each individual game, but if you continue to make choices with high expected value, it will inevitably converge to a plus in the long term.
This is the true nature of "skill" in Mahjong.

When you peek into the thought processes of professional mahjong players, you see that they are constantly weighing 'how this tile choice will change future risks and expected point values' rather than just 'whether I can win with this hand.'
They do not obsess over a single game, but keep their eyes on the positive balance of the entire half-game, and even the entire season.
This is exactly the same attitude as stock investors who do not get swayed by individual price movements, but judge their success based on the returns of their long-term portfolio.
Both investing and mahjong are dominated by randomness in the short term, but in the long term, the results are determined by whether or not you can consistently make decisions with high expected values.

On the other hand, mahjong has a decisive difference from pure sports.
Unlike competitions such as the 100-meter dash or tennis, where ability is almost directly linked to results, mahjong always has a variable called 'uncertainty' built into it.
This uncertainty is what leaves a certain chance of winning for beginners, while at the same time, it serves as an endless theme of exploration for professionals: 'how to manage uncertainty and maximize expected value.'
Luck in the short term, skill in the long term. This simple structure is the reason why mahjong can be called an intellectual game rather than just a form of gambling.

Chapter 4: Four Ways of Thinking Useful in Life

The reason why mahjong is not just entertainment and is supported by top executives is that the thinking methods polished at the table can be applied directly to decision-making in work and life.
Here, we will delve into four representative ways of thinking with concrete examples.

1. Expected Value Thinking

Expected value thinking is a way of judging things not by immediate results, but by the 'average return when repeating that choice.'

For example, in mahjong, there are often situations where you have a tile that would complete a high-scoring hand, but the probability of that tile appearing is very low, and the risk of dealing into another player's hand while waiting is much higher.
Emotionally, you want to aim for a 'come-from-behind victory,' but if you think in terms of expected value, you will often find that it is more profitable in the long run to steadily break up your hand and play it safe.

This is the exact same structure as investment decisions in business.
Suppose a new business project has a 'huge potential if it hits, but a 5% success rate.'
If you look only at the expected value, there may be cases where it is not worth the challenge, but if the loss in case of failure is limited and the return in case of success is extremely large, the expected value may be positive, making it a challenge worth taking.
The important thing is to develop the habit of judging by numbers that multiply probability and return, rather than by the impression that something 'seems big.'
By continuing to play mahjong, you naturally acquire this training of 'judging by numbers, not emotions.'

2. The Courage to Withdraw

In mahjong, there is a technique called 'folding' (or 'ori').
Even if your hand is close to winning, if another player has declared 'riichi' and you are forced to discard a dangerous tile, this is the strategy of giving up on winning, choosing only safe tiles, and avoiding dealing into another player's hand.

Beginners tend to obsess over winning, thinking, 'I've come this far, so I shouldn't give up.'
However, the stronger the player, the more they can decide to let go of their previous investment (time, tiles, progress of the hand) the moment they judge that the situation has turned bad, minimizing the damage.
This is the very definition of the business concept of 'not being trapped by sunk costs.'

Costs and efforts already invested should not really matter for future decision-making, but humans are inevitably pulled by the emotion of 'it would be a waste.'
Like continuing a project that is constantly in the red because 'I've done this much,' or being unable to cut ties with an incompatible business partner because 'we've known each other for years.'
The mahjong technique of 'folding' also serves as training to escape these psychological traps of human nature.

3. Thinking from the Opponent's Perspective

You cannot win at mahjong by only looking at your own hand.
The technique of 'reading'—inferring what tiles other players want and what hands they are aiming for based on their discards and calls—is essential.

This is essentially the same as the idea of 'thinking from the other party's position' in negotiations and marketing.
In sales, you build proposals starting from 'what the other party really needs' rather than 'what I want to sell.'
In negotiations with a boss, you think about 'what benefits this proposal has for them' rather than just 'my own demands.'
The more people train to read other players' hands in mahjong, the more they naturally develop the habit of imagining what the other person is thinking, fearing, and aiming for in daily communication.

Furthermore, the interesting thing about mahjong is that 'reading too much' can also lead to failure.
Being overly cautious about an opponent's hand and becoming unable to advance your own—a state known as 'folding too much'—will also lower your win rate in the long run.
The sense of balance between thinking from the opponent's perspective and maintaining your own strategy is another important lesson that mahjong teaches.

4. Resilience

In mahjong, there are days when you get good starting hands, but there are also inevitably 'unlucky days' when nothing goes right.
What is important here is the mental recovery power to remain calm even in a bad flow and switch to the next move or the next game—in other words, resilience.

If you suffer a crushing defeat in one game and let it drag on, causing your judgment in the next game to become sloppy, the damage will only expand further.
Conversely, players who can reset their emotions and think, 'that game was that game, this is a new one,' demonstrate stable strength in their long-term results.

This is the exact same structure as how one faces failures and troubles at work.
The way a long-term career is built changes significantly between someone who lets a single mistake or failure drag them down and disrupt their subsequent judgment, and someone who can accept the failure and calmly think about the next move.
Because mahjong is a game where it is impossible to keep winning, it repeatedly trains one of the most important skills in life: 'how to recover after a loss.'

Chapter 5: How the M.League Changed the Image of Mahjong

When people hear the word "Mahjong," many may think of the smoky atmosphere of a mahjong parlor or its gray-area reputation as a form of gambling.
Although professional mahjong players existed, it was difficult to make a living solely from it, and for a long time, the reality was that it was a "competition that was hard to establish as a profession."

What significantly changed this image was the professional league "M.League," which was launched in July 2018.
Founded by CyberAgent President Susumu Fujita, with Saburo Kawabuchi, the first chairman of the J.League, serving as the supreme advisor, this league set clear goals for turning mahjong into a professional sport and refreshing its image accordingly.
Affiliated players are guaranteed an annual salary, and there are prize pools for team championships and individual titles. To dispel the "gambling" aspect of mahjong, a system is strictly enforced where no money changes hands during the matches themselves.

Players belong to existing professional organizations such as the Japan Professional Mahjong League or the Saikouisen Mahjong Association, and are drafted into teams through the M.League's unique draft system.
Teams are operated by corporate sponsors, and the entry of companies from diverse industries—including television stations, IT companies, and game manufacturers—has helped boost the image of mahjong.
A 10th team will join in the 2025-26 season, further expanding the scale of the entire league.

Another feature of the M.League is its mixed-gender team composition.
Seeing female professionals sit at the table on equal footing with male professionals and compete based on skill has significantly rewritten the traditional image of mahjong.
Furthermore, matches are broadcast live with commentary and analysis on platforms like ABEMA, allowing viewers to enjoy the same sense of realism as a sports broadcast.
By providing real-time commentary on every move the professionals make, even viewers who do not know the rules can easily follow the excitement of the tactical play, which has resulted in the birth of a new culture of "watching" mahjong.

Through the accumulation of these efforts, the social standing of mahjong is steadily shifting from "gambling" to "e-sports that test intelligence."

Chapter 6: Why It Was Difficult for AI to Master

In the worlds of Go and Shogi, the era where AI overwhelms top human players has already arrived.
However, mahjong possesses a fundamentally different kind of difficulty compared to these games, and for a long time, it was considered a "difficult game to master" by AI researchers.

Go and Shogi are "perfect information games" where all information on the board is visible to the players.
The positions of the opponent's pieces or stones are all visible, and the game becomes a battle of how deeply one can read ahead based on that information.
On the other hand, mahjong is an imperfect information game where:
"Information other than your own hand and discards"
"What tiles the other players have"
"What tiles remain in the wall"
are all hidden.
The dimension of difficulty is fundamentally different in that decisions must be made amidst hidden information.

And mahjong has unique difficulties that Go and Shogi do not have.
There are four players instead of two.
The rules for calculating scores are extremely complex.
And one game consists of multiple rounds (eight rounds in typical online play), meaning one cannot measure final strength based on the score of a single round alone.
Tactical maneuvers frequently occur, such as a player in the lead intentionally letting the player in last place win to prevent the player in second place from gaining points.
The difficulty of evaluation is completely different from games like Go or Shogi where "victory or defeat" is decided simply.

The mahjong AI "Suphx (Super Phoenix)," developed by Microsoft Research Asia (MSRA), took on these challenges in earnest.
In March 2019, Suphx entered "Tenhou," one of Japan's largest online mahjong sites.
Since its opening in 2006, Tenhou has made all match records and tile logs public, providing an excellent environment as learning data for AI.
Suphx played over 5,000 matches at the "Tokujo" table, where players of 4th dan or higher gather, and in June of the same year, it became the first AI to reach "10th dan," the highest rank on Tenhou.

Its strength is also reflected in the numbers.
On Tenhou, an indicator called "stable dan" is used to measure skill by eliminating the element of luck, and Suphx's stable dan is an average of 8.7 dan or higher. Given that the average for top human players with about 10,000 games of experience is around 7.4 dan, this is a performance that clearly surpasses the top tier of humans.
Compared to the stable dan of around 6.5 for "Bakuchi," developed by the University of Tokyo, and "NAGA," developed by Dwango, which had participated in Tenhou before that, Suphx's leap was remarkable.
Supporting this strength were unique algorithms developed to address the specific challenges of mahjong, such as a learning method called "Oracle Guiding," which assumes the AI knows all hidden information while repeating self-play, and reward design that appropriately converts the score fluctuations of eight rounds into evaluations for each individual round.
It has also been reported that Suphx's playing style was characterized by steadiness, with a low rate of dealing into other players' hands and a low probability of finishing in 4th place.

The emergence of Suphx was a major step forward not only for mahjong AI research but for AI research as a whole regarding "decision-making under imperfect information."
Many real-world problems, such as autonomous driving and financial investment, require judgments in uncertain situations where information is hidden, just like in mahjong.
Isn't it an interesting fact, even for non-mahjong fans, that mahjong—a "mere tabletop game"—has actually become a perfect testing ground for cutting-edge AI research?

◆ Life is not determined by the "dealt tiles"

When playing mahjong, I sometimes think this.
The starting hand is bad. The draws are bad. No matter what I do today, it doesn't go well.
However, those who have been playing mahjong for a long time know.
That the quality of the starting hand is merely the entrance to that round.

Even from a similar starting hand, one person finds the shortest path to winning, while another breaks down their hand to focus on defense and minimizes the damage.
How you accept that hand and how you play it out affects the result far more than the bad starting hand itself.

I think this applies directly to our lives as well.
The environment we are born into, the talents we are given, and the timing that comes our way are all different "starting hands" we receive when we begin the game.
You cannot choose that starting hand yourself.
However, how you combine those tiles, what kind of hand you aim for, and where you attack and where you defend is left to your own hands until the very end.

The person who draws a good starting hand does not always win, and even from a bad starting hand, someone who persistently rearranges their hand may reach a win in the end.
The reason mahjong has captivated people for over 100 years may not just be the fun of pure chance, but because it encapsulates a story common to everyone's life: "how to make the most of what you are dealt."

The next time you sit at a mahjong table, or see a topic about the M.League in the news, try to remember this perspective for a moment.
It will surely change not only the way you look at the tiles on the table, but also the way you look at your daily choices, just a little bit!

If you found this article helpful, I would be happy if you could "like" or follow me!
See you next time...

I write about various things from my daily life as a substitute for a diary.
Please read my previous article as well if you have the time.