In 1676, the descendant of a shinobi clan compiled the knowledge of 49 schools of espionage – and it turned out that the arts of shadow were mostly arts of reading people.

Imagine opening the most comprehensive surviving ninja manual in the history of Japan. Five hundred pages. Twenty-two volumes. You expect instructions for throwing shuriken, recipes for poisonous gases, blueprints for secret passages inside castle walls. And you stumble upon two full volumes about what it means to have a “correct heart” – and why without it, none of these techniques will work. Then four more volumes on how to read people from their face, posture, and the way they walk. Three more – on the art of being nobody: how to disguise yourself as a wandering monk, a merchant, a street juggler, and become so unremarkable that nobody remembers you. The ropes, hooks, and lockpicks will have to wait.

This is Bansenshūkai (万川集海 – “Ten Thousand Rivers Flowing into One Sea”) – a compilation of knowledge from the shinobi clans of Iga and Kōka provinces, written down in 1676. Thirteen of its twenty-two volumes deal with the human mind: the psychology of manipulation, recognizing emotions, building trust, undermining loyalty, and – above all – the art of looking so ordinary that a guard’s eye slides over you like over furniture. Tools and weapons make up the minority. The shinobi’s greatest weapon was understanding what people fear, what they desire, and what will lure them into forgetting caution.

And the most interesting part is where Fujibayashi Yasutake (藤林保武) got all this knowledge. Not from books – from people. From fathers, grandfathers, and great-grandfathers who for generations had infiltrated castles, military camps, and daimyō residences, returned alive, and passed down to their sons one principle: before you enter a hostile fortress, enter the hostile mind. Bansenshūkai is the record of that experience – not of a single man, but of an entire culture of generations of spies who knew about fear, greed, vanity, and trust things that Western social psychology did not arrive at until the twentieth century. Or not at all. Forty-nine schools. Hundreds of missions. All distilled into one question: how do you get inside the mind of a specific person so that they do what you want of their own accord – and remain convinced it was their own idea?

“Ten Thousand Rivers” – where this book came from

The title Bansenshūkai sounds poetic – “The Sea into Which Ten Thousand Rivers Flow” – but the poeticism is deliberate. Fujibayashi was not creating his own system. He was gathering streams: techniques, doctrines, battlefield experiences, and the philosophy of dozens of ninjutsu (忍術 – literally: “the art of concealment,” or even more literally: “the art of enduring what cannot be endured”) schools scattered across two neighbouring provinces – Iga and Kōka – and channelling them into one sea. According to the records at the Iga-ryū Ninja Museum, the compilation encompasses the traditions of forty-nine separate schools.

The year is 1676. Japan is ruled by the fourth Tokugawa shōgun – Ietsuna. Peace has reigned for half a century. Swords rust in their scabbards, and young warriors do not know what a siege is because they have never seen one. For the shinobi clans, peace is a catastrophe of a different kind than war. In war, people die, but knowledge passes to the next generation because it is needed for survival. In peace, people live, but knowledge dies because nobody sees a reason to remember it.

Fujibayashi Yasutake understood this better than anyone. He was a descendant of Fujibayashi Nagato-no-kami (藤林長門守) – one of the three legendary jōnin (上忍, “senior shinobi”) of Iga province, alongside Momochi Sandayū and Hattori Hanzō. Iga was no ordinary province. For most of the Sengoku period it functioned as an autonomous republic of warrior-farmers known as Iga Sōkoku Ikki (伊賀惣国一揆) – a free confederation of local warrior families who had no daimyō above them and governed themselves. It was not a nest of spies – it was a state within a state, and espionage skills were its most valuable export.

That independence was ended by none other than Oda Nobunaga. In 1579, his son Nobukatsu attacked Iga on his own initiative – and was driven back by guerrilla strikes that sent his army fleeing the province in panic. Nobunaga was furious at his son, but even more furious at Iga. Two years later, he returned in person with forty thousand soldiers. The entire population of Iga numbered around one hundred thousand – including the elderly, women, and children. Villages were razed to the ground, and everyone who could be killed was killed. Those who survived scattered across Japan.

But they survived. The Hattori, Momochi, and Fujibayashi families found refuge with Tokugawa Ieyasu. When Tokugawa unified Japan, the shinobi from Iga and Kōka were given a new role – castle guards, escorts, gardeners on the shōgun’s grounds. A noble retirement that, generation by generation, looked increasingly like oblivion. And it was precisely at this moment – when the world of the shinobi was becoming a legend even for the descendants of those very families – that Fujibayashi Yasutake sat down and began to write.

He wrote in kanbun (漢文) – an archaic Sino-Japanese literary style so difficult that modern-day Japanese cannot read it without specialist training. The first complete version in modern Japanese – with commentary by the historian Nakashima Atsumi – did not appear until the twentieth century. The English translation by Antony Cummins and Yoshie Minami was published in 2013. And in June 2022, in a storehouse of the Kazuraki temple in Shiga Prefecture, researchers discovered the manuscript of Kanrinseiyō (間林清陽) – a source text that Fujibayashi had drawn upon during his compilation. The copy dated from 1748. A source he had mentioned on the opening pages of Bansenshūkai, whose existence no one had been able to confirm for centuries – finally emerged from the darkness.

The architecture of the manual – what the proportions tell us

When you open a technical book, the table of contents tells you more about it than any single chapter. So let us look at the proportions. Bansenshūkai consists of twenty-two volumes grouped into six sections. Volume One is an introduction: history, a table of contents, and a question-and-answer section on the essence of ninjutsu. Then the real substance begins.

正心 seishin – “the correct mind”: two volumes on the inner philosophy and psychology of the shinobi. 処置 shochi – “guidelines for commanders”: four volumes on how to recruit spies, manage them, read people, and exploit their weaknesses. 陽忍 yōnin – “open infiltration”: three volumes on the art of disguise, building false identities, entering enemy camps in broad daylight. 陰忍 innin – “hidden infiltration”: five volumes on stealth, break-ins, lock-picking, night attacks. 天時 tenji – “conditions of heaven”: two volumes on astrology, meteorology, and divination. 忍器 ninki – “shinobi tools”: five volumes on ropes, hooks, climbing gear, water crossings, incendiaries, and poisons.

The mathematics is merciless. Inner philosophy and psychology – two volumes. The psychology of commanding and managing people – four volumes. The art of disguise, social manipulation, and building false identities – three volumes. A total of nine volumes on the human mind before we even get to creeping across rooftops. Add the five innin volumes, which are also largely about psychology – predicting guards’ behaviour, sensing the moment of inattention – and you understand what Bansenshūkai truly is. It is not a weapons manual. It is a manual for reading people that happens to contain a few recipes for gunpowder.

A blade over the heart – seishin

Before Fujibayashi writes so much as a single word about techniques, he begins with foundations. The first two volumes bear the title seishin (正心) – “the correct mind” or “true sincerity of the heart.” But to grasp the depth of what Fujibayashi means, it is worth stepping back and looking at the character nin (忍) itself – the one that gives the entire tradition its name.

The kanji 忍 is composed of two elements: 刃 (yaiba, blade) above 心 (kokoro, heart). Literally – “to hold a blade over the heart.” To endure. To conceal pain. To suffer and show none of it. As the French linguist and ninjutsu researcher Kacem Zoughari wrote: this character describes the state of a person who suffers, endures misfortune, and must conceal it – honing their thoughts like the edge of a sword, remaining in constant readiness, shaping the heart to withstand hardship. This is not the description of a warrior. It is the description of a person who has subordinated their entire psyche to a single mission.

And this is exactly what Fujibayashi writes in Volume Two (I should note that in this particular case I base all translations on the English-language version by Cummins):

“The essence of Nin is the correct heart and mind. The elements of nin are: covert activity, information gathering, disguise, and surveillance. Without first having a correct heart, it is impossible to take advantage of strategy.”

He then lists the five virtues of the shinobi: wisdom, virtue, sincerity, courage, and asceticism. The list originates from Sun Zi, but Fujibayashi does not copy it mechanically – he translates it into the language of shinobi experience. Following the original Sun Zi, he does not understand asceticism as self-mortification but as the ability to relinquish comfort at any moment; he does not understand courage as bravado but as the readiness to act when everything inside you screams to flee.

Momochi Sandayū – the legendary jōnin from Iga, whom Fujibayashi quotes with evident respect – put it even more sharply: “Ninjutsu is not something that should serve personal desires. It is something to be used when there is no other way out – for the good of the country, for one’s lord, or to save one’s own life.” And also: “Whoever deliberately uses these skills for personal gain will certainly meet with failure.”

This is not moralizing. It is pragmatism. Seishin is a training programme in emotional regulation – not because emotions are bad, but because emotions betray. A shinobi who allows himself fear will change his breathing rhythm. One who is carried away by anger will raise his voice. One who craves a reward will start to rush. Each of these reactions is a signal, and every signal is death. In modern terms: Fujibayashi describes the training of executive functions and emotional self-regulation – precisely what cognitive psychology did not begin to study systematically until the second half of the twentieth century.

The art of being nobody – yōnin

Bansenshūkai divides all of ninjutsu into two great branches. The first is yōnin (陽忍) – the “bright side of shinobi/infiltration.” The second is innin (陰忍) – the dark side. The division refers to the Chinese concepts of yō and in – the light and dark side (better known in the West as “yin and yang”). Yōnin means espionage in broad daylight, in disguise, among people, with a smile on your face. Innin means operating at night, in hiding, with no contact with the enemy. And paradoxically, yōnin was considered the harder art – because nocturnal stealth requires patience and physical skill, but daytime disguise requires something far rarer: total mastery over one’s own identity.

Fujibayashi writes: “In ninjutsu there are yōjutsu (陽術) and injutsu (陰術). Yōjutsu is the method of entering enemy territory by means of a clever stratagem. Injutsu is infiltration unnoticed, through use of personal disguise.” But then he adds something that reveals the depth of this approach: “When you disguise yourself as someone with a particular trade, you must know that trade. If you try to imitate the appearance and speech but do not know the craft, your deception will quickly be uncovered.”

Here we enter the heart of the matter. The classic list of shichihōde (七方出, “seven disguises”) – described in both Bansenshūkai and Shōninki (正忍記) by Natori Masatake – lists seven identities a shinobi could assume: a komusō monk with a bamboo basket over his head, a wandering Buddhist monk (shukke), a mountain ascetic (yamabushi), a merchant, a street performer (hokashi), an actor (sarugaku), and – the last and hardest – an ordinary person.

Each of these disguises was not merely a costume but a role. The komusō monk wore the distinctive straw basket tengai covering his face, played the shakuhachi flute, and had the right to move freely – but the shinobi had to actually know how to play that flute, because false notes aroused suspicion faster than a false face. Yamabushi could carry weapons – a sword or naginata – without provoking questions, but assuming this role required knowledge of shugendō rituals, mantras, and behaviours typical of ascetics (as well as the right build). The street performer hokashi moved between towns giving shows with trained monkeys and juggling tricks – he had access to every marketplace in Japan. But he truly had to be able to perform these tricks professionally.

As we read in Bansenshūkai, however: the hardest disguise is no disguise at all. An ordinary person – a peasant, a labourer, a vendor at the market – has no alibi, no reason to be in a given place, apart from being so unremarkable that it occurs to no one to pay attention. In one of the shinobi clans, the final test looked like this: the student would don a disguise and board a ferry. After some time, the master would also come aboard, and then ask the ferryman whether he had noticed anyone suspicious. If the ferryman replied: “No, sir, I’ve been doing this job for years – if someone were suspicious, I’d have noticed” – the student passed. If he said: “Yes, there was a young man today, rather restless” – the student failed.

This is a fundamental psychological lesson confirmed by modern science through research into inattentional blindness: people do not register what fits their expectations. Daniel Simons and Christopher Chabris at Harvard proved it with the gorilla-on-the-court experiment – nearly half of observers failed to notice a person in a gorilla suit walking through the frame because they were busy counting ball passes. Fujibayashi described the same mechanism three hundred years earlier, except instead of a gorilla he used a peasant from Iga. Shōninki states it plainly: “The overriding principle of the shinobi is not to be discovered by others. Therefore you should equip yourself with such garments as will change your appearance.” But it is not about the garments – it is about perception.

A manual for reading people – shochi

The four volumes of shochi (処置 – “to manage and arrange,” or, as Cummins proposes: “A Guideline for Commanders”) are the most surprising part of Bansenshūkai – not because they describe techniques we do not expect, but because they describe them from a perspective we do not expect. Shochi is not addressed to the shinobi. It is addressed to his commander – to the samurai, the daimyō, the general who must know how to use spies. Fujibayashi says: even the best shinobi is useless if the commander does not understand how the human mind works.

Drawing on the thirteenth chapter of Sun Zi’s “The Art of War,” Fujibayashi presents five types of spies – gokan (五間): the local spy (kyōkan), recruited from among the inhabitants of enemy territory; the inside spy (naikan), planted among enemy officials; the double spy (hangan), an intercepted enemy spy turned to our side; the “doomed” spy (shikan), sent out with false information in the knowledge that if captured, he will betray nonsense; and finally the surviving spy (shōkan), the highest-grade agent who returns with intelligence.

Sun Zi provided the framework – Fujibayashi deepened it. In the shochi volumes, the question is not “what are the types of spies?” but “how do you recognise who is suited to which type?” And here the psychology begins. Fujibayashi describes how to assess a person’s character from their behaviour: from their posture, from the way they walk, from whether they look you in the eye or avoid your gaze. Whether they speak quickly (anxious, easy to intimidate) or slowly (self-assured, harder to manipulate). Whether they boast of wealth (greedy, susceptible to bribery) or live modestly (loyal or lazy – further investigation needed). This is proto-psychological profiling, conducted in the field, without questionnaires or scales – through observation and conversation alone.

But Bansenshūkai goes further still. It describes how to use emotions as tools. The Chinese medical and Confucian tradition recognizes the concept of the seven emotions – shichijō (七情) – joy, anger, sadness, fear, love, hatred, and desire. Fujibayashi treats them as a list of entry points into the human mind. A man consumed by anger makes rash decisions. A man consumed by fear accepts any promise of safety. A man consumed by greed loses his vigilance at the sight of gain. A man consumed by vanity will say too much if you flatter him. The shinobi does not fight the man. The shinobi fights by means of his weakness.

In Bansenshūkai there is a passage describing how a general whose soldiers were losing their fighting spirit to greed – they were more interested in plunder than in battle – ordered part of his own camp set ablaze and blamed it on enemy spies. In this way he used anger to overcome greed: the soldiers, furious at the supposed saboteurs, forgot about plunder and charged into attack. One emotion used as an antidote to another – Fujibayashi describes it with the precision of an analyst, not a moralist.

The sister text – Shōninki, written by Natori Masatake in 1681 – goes even further in these matters. Its second scroll is devoted to defence against enemy spies, understanding human nature, physiognomy, recognizing people’s true intentions, and planting false trails. The third scroll concerns one’s own emotional states and the emotional states of others. The two texts – Bansenshūkai and Shōninki – together form what can only be called a training programme in emotional intelligence, written three hundred years before that term was coined.

“One man can defeat a thousand”

Bansenshūkai returns to one idea like a mantra: “One properly deployed spy can destroy an entire army.” Fujibayashi writes this with full conviction – he consistently emphasizes that ninjutsu is the most effective method of military strategy, more effective than cavalry, five times more effective than a siege, because it acts not on soldiers’ bodies but on the commander’s mind. Destroy a general’s trust in his own men and his army will disintegrate on its own. As Volume One states: “If subordinates think differently from their commanders, defeats and losses will not be long in coming.”

The disinformation techniques described in Bansenshūkai are strikingly modern. Planting false crests on the battlefield to mislead the enemy about the identity of attacking units. Spreading rumours in the enemy camp – not random ones, but targeted: the kind of rumour that strikes at a particular commander’s weakness. Using turned spies to feed the enemy information that is eighty percent true – because those twenty percent of lies, hidden in a sea of truth, are undetectable.

Kevin Mitnick – the legendary hacker who in the 1990s broke into the computer systems of the best-protected companies in America – once said that the weakest link in any security system is the human being. Not the password, not the firewall, not the encryption – the person who can be talked into giving up a password because someone introduced themselves as a member of technical support. This is social engineering – the modern name for what Fujibayashi described three hundred years earlier.

Paul Ekman, an American psychologist, spent decades cataloguing micro-expressions – involuntary, lightning-fast movements of facial muscles that betray true emotions even when a person is trying to conceal them. He created the Facial Action Coding System (FACS), which became a standard tool for intelligence services. The fruit of his work is a systematic, scientific version of what the clans of Iga and Kōka passed from father to son for generations: the ability to read emotions from a face in a fraction of a second, in the field, under pressure, when the accuracy of your reading determines whether you make it home.

The dark side – innin

The five innin volumes – this is the part we picture when we think of ninja. Creeping through the night, breaking into residences, picking locks, surprise attacks. Fujibayashi provides detailed descriptions of climbing tools, water-crossing equipment – partly based on the experience of pirates – burglary tools for forcing doors, drilling holes in walls, and opening locks, as well as fire techniques – recipes for explosives, smoke bombs, poisons, and sedatives.

But even in these most “technical” volumes, the psychology never disappears. Fujibayashi writes about how to predict guards’ behaviour – when they are most tired (the hours after midnight), when their attention drops (after a shift change, when they relax with relief), which way the wind blows (because it may carry the sounds of a break-in to the guards’ ears). The section on breaking into buildings begins not with a description of tools but with a principle: “Before you decide to break into any house, study its gate and appearance – this way you will be able to choose the right tool.” Observation before action. Understanding before force.

Arson deserves a section of its own – not as a technique of destruction but as a psychological weapon. Bansenshūkai distinguishes between “main fires” – large blazes set at strategic points, brighter than sunrise, built from woodpiles two metres high – and “random fires,” ten smaller blazes lit dozens of metres from the enemy camp. The purpose of the “random fires” is not destruction. The purpose is panic, chaos, disorientation – soldiers do not know where the attack is coming from, how many attackers there are, which way to flee. The fire does not consume the camp. It consumes reason.

The honesty of a pragmatist – what Fujibayashi was not sure about

There is something in Bansenshūkai that sets this book apart from its era and makes Fujibayashi command respect even from a modern reader. When he reaches the two tenji volumes – devoted to astrology, divination from the Chinese calendar, onmyōdō (陰陽道, the esoteric yin-yang system) and determining auspicious days for missions – Fujibayashi does something surprising. He warns that these techniques are dubious.

He writes himself that divination “is not worthy of trust.” But then immediately adds: knowledge of these systems is useful when you are fighting a general who believes in them. Because if your enemy plans an attack on a day deemed auspicious by the Chinese calendar, you can predict the date of the attack without any spy – you only need to know his system of beliefs.

The same pragmatism shines through Shōninki, where Natori Masatake also cites Chinese literature on physiognomy and divination – and also with the caveat that these systems are worth knowing not because they work, but because others believe they work. It is a remarkably modern epistemological stance: do not believe in the system, but understand it – because the people you are trying to read do believe.

Bansenshūkai is a testament

One hundred and thirteen years after Bansenshūkai was written, three figures from Kōka – Ohara Kazuma, Ueno Hachizaemon, and Oki Moriichiro – set out on the long road to Edo. It is 1789; the French Revolution is turning Europe upside down, while in Japan the descendants of the Kōka shinobi are fighting for something far more modest: the restoration of their status and stipends. They bring with them a copy of Bansenshūkai and a sake cup as gifts for the shōgunate official Matsudaira Ukyōnosuke.

Matsudaira accepts the manuscript, examines it, appreciates it. Then he gives the delegation a symbolic handful of silver coins – far less than they need, more a parting gesture than assistance – and a small additional amount of silver to distribute among the remaining families. The delegation returns to Kōka with nothing. But the copy of Bansenshūkai they left in the hands of the shōgunate ended up in the archives. And it is there to this day – in the National Archives of Japan. It is this very copy that served as the basis for the English-language translation.

For more than two hundred years after Fujibayashi’s death, Bansenshūkai existed in a narrow circle of hand-copied manuscripts, carefully guarded by families who understood less and less what exactly they were guarding. After the Second World War, a small print run made it to public libraries. The edition sold out; the publisher did not reprint. For a long time, the only way to read Bansenshūkai was either to gain access to the original manuscript or to find a scan circulating online in the early 2000s – untranslatable for anyone who had not studied archaic Japanese.

It was Nakashima Atsumi – a historian of traditional martial arts schools and chairman of the Federation of Japanese Koryū Bujutsu – who prepared a version with scans of the original text, a transcription in modern Japanese, and a scholarly commentary. Then came Cummins and Minami with their English translation. And finally – in 2022 – Kanrinseiyō: the source Fujibayashi had drawn upon emerged from a temple storehouse in Shiga Prefecture after nearly three centuries of oblivion. It described forty-eight ninjutsu techniques – from lining sandals with cotton (to muffle sound while creeping) to fighting techniques for when surrounded by the enemy.

Iga, half-light, a brush

I imagine Fujibayashi Yasutake sitting in his house in northern Iga – where his great-grandfather Nagato-no-kami once controlled the territory bordering Kōga province. It is the summer of 1676. Through the window he can see the mountains that once guarded the autonomy of the shinobi republic. Now they guard the peace of gardeners.

Fujibayashi writes. Not for himself – he will never use these techniques, because there is no longer an enemy from whom he would need to disguise himself as a monk. Not for his lord – because his lord needs an accountant more than a spy. He writes for someone who does not yet exist. For some young person in the future who will open this text and understand that it is not about poisons or hooks – it is about the fact that his grandfathers knew things about human nature that the rest of the world would not arrive at for another three hundred years.

He merges forty-nine rivers into one. Each carried someone’s blood, someone’s wisdom, someone’s death at their post. Most of these people had no gravestones. Many did not even have known names that anyone could carve in stone – because their entire lives consisted of making sure nobody knew who they were. Fujibayashi gives them something that was meant to be merely a manuscript. It became a monument.

SOURCES

1. Cummins, Antony; Minami, Yoshie – “The Book of Ninja: The Bansenshūkai – Japan’s Premier Ninja Manual.”

2. Natori Masatake, 『正忍記』 (Shōninki), 1681. English translation: Cummins, Antony; Minami, Yoshie – “True Path of the Ninja.”

3. Nakashima Atsumi, 『完本万川集海』 (Kanpon Bansenshūkai), scholarly commentary. Shinjinbutsu Ōraisha, Tokyo.

4. Turnbull, Stephen – “Ninja AD 1460–1650,” 2003.

5. Zoughari, Kacem – “The Ninja: Ancient Shadow Warriors of Japan,” 2010.

6. 三重大学・山田雄司; 中西豪 – Announcement of the discovery of 『間林清陽』 (Kanrinseiyō) in the storehouse of Kazuraki temple, Shiga Prefecture, June 2022.

7. Ekman, Paul – “Emotions Revealed: Recognizing Faces and Feelings to Improve Communication and Emotional Life,” Henry Holt, 2003.

"Strong Japanese Women"

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    未開    ソビエライ

 An enthusiast of Asian culture with a deep appreciation for the diverse philosophies of the world. By education, a psychologist and philologist specializing in Korean studies. At heart, a programmer (primarily for Android) and a passionate technology enthusiast, as well as a practitioner of Zen and mono no aware. In moments of tranquility, adheres to a disciplined lifestyle, firmly believing that perseverance, continuous personal growth, and dedication to one's passions are the wisest paths in life. Author of the book "Strong Women of Japan" (>>see more)

Personal motto:

"The most powerful force in the universe is compound interest." - Albert Einstein (probably)

  Mike Soray

   (aka Michał Sobieraj)

未開    ソビエライ

 An enthusiast of Asian culture with a deep appreciation for the diverse philosophies of the world. By education, a psychologist and philologist specializing in Korean studies. At heart, a programmer (primarily for Android) and a passionate technology enthusiast, as well as a practitioner of Zen and mono no aware. In moments of tranquility, adheres to a disciplined lifestyle, firmly believing that perseverance, continuous personal growth, and dedication to one's passions are the wisest paths in life. Author of the book "Strong Women of Japan" (>>see more)

Personal motto:

"The most powerful force in the universe is compound interest." - Albert Einstein (probably)

Mike Soray

(aka Michał Sobieraj)

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