A Ninja's mission is to return alive from enemy territory and convey accurate information to the lord.
Let's learn about the information transmission techniques, memory techniques, and survival techniques needed to do this from various angles!

Fire techniques were a crucial element in warfare, capable of influencing the course of battle. In an era without electricity, fire was used not only as a weapon but also for lighting, signaling, and communication.

Explosive arrows loaded with gunpowder, grenade-like explosives, and landmines were effective in battle for burning down castles and camps and disrupting the enemy. On the other hand, matchlock guns, which produced sound, were reportedly only used by certain schools.

Approximately 80-90 cm in length. It was used to set fire to enemy residences and other structures.

Approximately 10 cm in diameter. A hōraku (unglazed clay pot) was packed with gunpowder and iron fragments to increase its explosive power.

Approximately 4 cm in diameter. Gunpowder was wrapped in dried straw and covered with torinoko-gami (a type of paper). It produced a loud bang and a large amount of smoke.

Torches and other lights were essential for nighttime activities. Depending on the gunpowder mixture and materials used, these lights were adapted to specific purposes, such as being resistant to wind and rain or lasting for multiple nights.
"Gandō" (Portable Lantern)
The inner ring rotates side to side, keeping the candle stable and preventing it from tipping over, thus ensuring the flame does not go out.

Smoke signals made from wolf dung were visible up to 5 km away in good weather, although they couldn't be used in rainy conditions.

Although the introduction of firearms and gunpowder is traditionally said to have occurred in 1543, it is believed that people from the continent, who had settled in regions like Iga and Koga, were familiar with gunpowder even before this time. Some theories suggest that they may have been using gunpowder prior to 1543.

The Bansenshukai records a total of 208 types of gunpowder ingredients, mainly minerals, plants, and animal products. Various blending methods are introduced, demonstrating the ninja's expertise in handling fire.

Saltpeter, sulfur, alum, iron sand, etc.

Camphor, bamboo tubes, charcoal, mugwort, pine resin, pine powder, vegetable oil, paper, borneol, glue, powdered green tea, etc.

Rat dung, cow dung, wolf dung, horse dung, etc.

Aged sake, mouth medicine, etc.

Gunpowder is made from ingredients such as saltpeter, sulfur, and charcoal, but saltpeter, the key component, does not naturally occur in Japan's warm climate. Ninjas possessed the knowledge to produce saltpeter from waste. By mixing animal dung with urine, burying it in soil, and allowing bacteria to break it down, they were able to create saltpeter.

The smoke bomb Tori no Ko, used by ninjas when pursued by enemies, was a firearm crafted by weaving dried straw and packing it with gunpowder. Wrapped in torinoko-gami (a type of Japanese paper) with a fuse attached, it produced a loud bang, intense flames, and thick smoke. Ninjas would take advantage of the enemy's surprise and confusion to escape in the cover of smoke.

The Bansenshukai describes making an egg-shaped bundle about 4 sun (approx. 12 cm) with straw and filling it with gunpowder. In the experiment, regular black powder (saltpeter, sulfur, charcoal) was used, and gunpowder was packed inside an empty eggshell instead of straw. The result produced intense flames and a large amount of white smoke, demonstrating that it had enough potency to blind the enemy's vision effectively.

Since gunpowder ignites instantly, the timing for lighting the fuse and the method of carrying the fire source were crucial. It's said that ninjas practiced repeatedly to ensure they could use it effectively in real situations.

Aburidashi (invisible ink) involves using a liquid (such as citrus juice or soybean extract) that becomes colorless when dry. Writing with this liquid on paper, the text becomes visible only when heat is applied, due to a reaction between cellulose in the paper and the acids or sugars in the juice, which makes the treated areas burn faster when heated.
Aburidashi was used to send secret information to allies without anyone else being able to read it, making it an advanced method of information protection using the cutting-edge science of the time.

Experiments using "soybean extract" and "doburoku" (cloudy sake) mentioned in ninja manuals were successful. The presence of sulfate ions and other ions in soybean extract, and the high sugar content in doburoku, likely contributed to the results.
Further experiments with citrus juice showed that ink suitable for aburidashi can be created if it has multiple properties such as: high sugar content, acidity, high potassium ion concentration, and sulfate ions. This reveals that various scientific components can be used to make invisible ink.

There is also a method called mizudashi, where the text appears when soaked in water!
Note: This experiment was conducted by Professor Susumu Kato (Specially Appointed Professor, Mie University).

Smoke signals (noroshi) were a communication method using wolf dung. A hole was dug in the ground, and a mixture of wolf dung and pine resin on straw was set alight. A large bamboo tube, with a hollowed-out section, was placed in the center to allow the smoke to rise straight up. According to the Nihon Shoki, smoke signals were recorded as being used in 664 AD in Tsushima, Iki (Nagasaki Prefecture), and Tsukushi Province (Fukuoka Prefecture). During the Sengoku period, they were used by feudal lords as a means of communication within their controlled areas.

Wood and plants containing flammable oils and moisture, such as pine, cedar, cypress, and mugwort, were often used because they produced white smoke when burned. It is hypothesized that specific burning methods could slow the combustion speed compared to regular fires. Experiments with wolf dung showed that it produced an extremely foul odor, undetectable even by smell meters.

In 1988, an experiment was conducted to see whether a "relay of smoke signals" or the "Shinkansen (bullet train)" would reach a destination faster over a distance of 250 km from Osaka Castle to Onomichi in Hiroshima Prefecture. The bullet train arrived in 1 hour and 48 minutes, while the smoke signal relay arrived in 1 hour and 58 minutes, passing through 29 locations along the way.

It's amazing that information could be transmitted at nearly the speed of the bullet train in a time without the internet!
Note: This experiment was conducted by Professor Susumu Kato (Specially Appointed Professor, Mie University).

While direction can be determined by observing the sun and celestial bodies, it is influenced by weather conditions. Therefore, ninjas used a handmade "compass." The kishaku, made from a thin iron plate measuring 3 to 4 cm in length, had the property of rotating to point in a specific direction when floated on water. If it was difficult to float on water, it is believed that they placed it on thin paper for use.

The kishaku utilizes the principle of "thermal remanent magnetization," where an iron needle becomes magnetized when heated and then cooled. However, it is difficult to make, as the tip must be oriented toward the correct direction (south or north) during the cooling process.

Sounds such as animal calls, the clapping of wooden sticks, and the smoke from cooking were all useful references for determining the time. The Big Dipper, which revolves around the North Star in 24 hours, moves 15 degrees every hour. By remembering the position of the stars at the start of a mission, ninjas could keep track of the passage of time. The "cat's eye clock" described in the ninja manual Bansenshukai is said to have originated in China and was brought to Japan during the Muromachi period.

The success of infiltration missions is greatly influenced by the timing of entry. Furthermore, when multiple ninjas are involved in a mission, any mistake in timing could jeopardize the operation, making it essential for ninjas to have an accurate understanding of the time.

To ensure that life-threatening information could be reliably brought back, unique information transmission techniques were developed.

A cipher based on the Chinese "Five Elements Theory," which states that everything in the world is composed of the five elements: wood, fire, earth, metal, and water. By arranging kanji characters for colors such as blue, yellow, red, white, black, and purple, a unique set of 48 characters was created. These were combined with the Iroha song to convey information as effectively as standard letters.

In addition, there were instances where the Iroha was replaced with numbers and written on paper. Another method involved shifting the reading of each character, which required mutual understanding of the rules in advance with the communication partner, making it important to exercise caution.

This was a method of information transmission among ninjas using rice grains dyed in five colors: red, blue, yellow, black, and white. By combining different colors and quantities, they created ciphered messages, assigning specific meanings to each of the five colors based on the mission. Additionally, in a technique called "nashirushi(marking each name)," when multiple ninjas acted together, they would designate their "assigned color." At a fork in the road, each would place their assigned color in the direction they chose to signal their intended path to their companions.

To memorize the number of people, ninjas would pre-associate numbers with parts of their body, such as "head = 1," "forehead = 2," "eye = 3," etc. For example, if "there are 231 enemy soldiers," they would remember it as "enemy = forehead, eye, head."

Memories associated with emotions like "surprise" or "joy" are easier to retain, so there was also a method of memorizing through exaggerated imagery. For example, to remember "there are 231 enemy soldiers," one might visualize the enemies as having faces twice the normal size, three eyes, and one horn on their heads, creating a vivid and exaggerated mental image to aid memory.

This method involved inflicting wounds on one's body with a sword while visualizing the information to be remembered. It leveraged the phenomenon where pain and fear leave a strong impression in the mind, allowing for long-term retention of important information through trauma. However, it was a method that could not be used lightly.

The mechanism of human memory is said to involve the hippocampus, which is located in the limbic system of the brain. Information such as qualifications and auditory inputs is gathered in the brain's hippocampus and stored for a certain period. After that, memories are sorted, and those that are intended to be retained longer are sent from the hippocampus to the cerebral cortex, where they are stored as long-term memories.

Ninjas developed many methods to conceal themselves from enemies in order to survive and return with information.

By tucking in the arms, legs, and head to curl up in a ball face down and breathing quietly, one can eliminate their presence. Covering the head helps conceal the whiteness of the skin. Additionally, blocking one's own view by covering the face can help suppress feelings of fear.

By wearing large leaves, such as lotus leaves, on the head while submerging the body in water with only the head above the surface, ninjas exploit the blind spot of "surely, there can't be a person underwater." Although the clothes become heavy from the water, this method protects against harmful creatures like snakes that might be in the water.

By covering the face with the sleeves of a kimono and standing in the shadows of a wall or tree, ninjas took advantage of the preconception that "intruders are hiding" and concealed themselves by blending in with the tree.

By climbing into a tree to hide, ninjas could easily observe the movements of their enemies from their concealed position. This technique was also useful during reconnaissance missions.

Ninja teachings include specific methods for hiding information even at the time of death, emphasizing that when committing suicide, one should leave no trace-even the bones should be obliterated, leaving only a charred and unrecognizable corpse. The concept of "leaving no traces even in death" truly embodies the essence of being a "shinobi."

By the way, the animal referenced in "Tanuki-gakure," the tanuki (raccoon), is actually not good at climbing trees. The name serves as a reminder of the importance of taking advantage of the perception that "there cannot possibly be a raccoon in a tree."

• To avoid being spotted by the enemy, assume the "uzura-gakure" position in front of a stone!
• After you're done, switch with the next person!

"Uzura-gakure" is a technique where one curls up face down, pulling in their limbs and head while breathing quietly to eliminate their presence.

• Submerge yourself and try to peek out from the water surface! Don't forget to place a lotus leaf on your head!
• After you're done, switch with the next person!

"Kitsune-gakure" is a technique where one wears a lotus leaf on their head and hides underwater, with only their head above the surface.

It safeguarded not only the lives of the ninjas but also a "secret manual on gunpowder."

At first glance, it appears to be an ordinary wall, but it has a rotating structure that allows one to escape to the other side. It only rotates 180 degrees and is designed not to move even if pursuers push against it in the same manner.

A secret storage space beneath the floorboards. When stepping on the edge of the floorboard, the opposite side would rise, allowing one to retrieve hidden items such as swords.

It appears to be just a shelf under normal circumstances, but once the latch is removed, it transforms into a staircase. There were also secret passages leading from inside to an outdoor well.

It appears to be an ordinary wall, but inserting paper or similar objects into the gap releases the lock and opens the door. When enemies attacked the mansion, ninjas would escape through here. If they fled quickly, it would remain undetected where they had escaped from.

The range and accuracy of firearms greatly depend on the composition of the gunpowder. To maintain an advantage for their own country, the ninjas' knowledge of gunpowder was classified information that could not fall into enemy hands.

• Enter the ninja mansion and look for places where you can peek outside!

• Pop Your Face Out from the Hanging Scroll and Take a Photo!