"Pay attention to any possibility that arises before you" - Natori Masatake (Shoninki)
To counter yo-nin, the Giyoshu military manual advises driving away any beggars that come to a gate or guard house and keeping away anyone from other territories that approach important guardhouses, even if they are relatives.
Kishu-Ryu Yo-nin Edit
"If you are detected, you should leave it to fate and do not give in to fear, life is found within death" - Natori MasatakeNatori Masatake, author of the Shoninki shinobi manual, advises shinobi to walk by the gate of a mansion or castle they will infiltrate with a phony intention in mind a few times. One false intention given is asking for medicine, hot water or cold water while faking an illness. Natori recommends faking the following illnesses; omushi (stomachache), kakuran (sudden vomiting), gansho (food poisoning), epilepsy, diarrhea, etc. He advises going the night without sleep, getting a moxa treatment, fasting, growing one's beard, hair and nails, not bathing, wearing less clothing and a hachimaki headband with a thin piece of string to help the shinobi's performance. Natori suggests practicing this skill carefully. Although he advises against pretending to be drunk.
After getting what the shinobi asked for he should pretend to have recovered and went to thank the person who helped them to get acquainted. At a later date, the shinobi should come back to give the occupants gifts and show gratitude in order to flatter them. Praising their children is a good way to get invited in, according to Natori. He also tells us who the shinobi should give gifts to in order; first the master's wife, then his favorite servant, and finally the master himself. The shinobi would converse with the building's occupants to gain the information he needs.
The Shoninki also advocates estimating the area of a place, and then multiplying it. It also details a technique used to count the number of houses within a compound. Two bags of a certain number of pebbles or beans would be tied up in each sleeve. The shinobi would discard a pebble or bean for each house. More pebbles would be put in each bag than the amount the shinobi expects he would find. Beans or pebbles from the left sleeve would be discarded for unoccupied houses, and beans or pebbles from the right sleeve would be discarded for occupied houses. Afterwards, the shinobi would count the number of items in each bag and subtract it from the original number.
This technique could also be applied to counting troops but with a higher number of bags for the different troops. The shinobi would pick a spot where the troops would have to walk in a single file. Another technique recounted by Natori is pretending to be a merchant accompanying the army for a few days. The shinobi would only speak with the servants and he would do favors for them in order to be well liked by the lower-ranking people.
In another chapter Natori advocates avoiding checkpoints, even if the shinobi has to walk for miles, and if necessary using the guise of a shukke medicine monk, yamabushi priest, merchant, pilgrim, or as anyone the shinobi sees fit to disguise himself as. Natori also recommends traveling with with two or three people to look less suspicious and mastering the art of dakko (understanding all the local customs and dialects).
The next chapter speaks of a technique called "the way of cattle and horses" in which a commander would send a shinobi to the enemy general as a messenger or servant accompanying an envoy. The shinobi would then walk freely among his enemies, being led and guided by them, in order to gather information. He could then use his wits to make up an excuse to investigate further. The Shoninki provides a few examples such as having a relative in the area and pretending to visit them or faking an illness.
In a different chapter, Natori claims that the best areas for information gathering are shrines and temples. He recommends giving priests generous donations in order to have them offer meals and hospitality. This is when the shinobi would get the priest drunk and probe him for information. Besides getting the priests drunk, there are other ways of getting information from men of the cloth. For example, hinting at your willingness to help in a project financially or loosening their tongues by having them speak about their hopes and dreams. Other areas good for information gathering are ageya, licensed houses where courtesans get appointed with clients, public baths, keiseiya brothels and gambling dens.
Natori also lists the optimum times to infiltrate an enemy's camp:
- When lower-ranking soldiers are cutting down trees and bamboo
- While they are setting up camp
- On the night after a battle
- During a rain storm
He mentions blending in with the lower-ranking soldiers and not the samurai. When scouting ahead, Natori advises speaking to people in the area of infiltration using their dialect. He also suggests listening carefully to secure the enemy's password. Natori then goes on to list how people used to counteract this technique:
- Tachisuguri Isuguri (立ちすぐり居すぐり): This is the method of standing up or sitting down when a password is given to add security and to identify enemy spies
- Aijirushi (相印): Markings, emblems or signals
- Aikotoba (相言葉): The addition of supporting combination passwords
Natori advises moving from one place to another often to help avoid being followed. Following this, he mentions toki no sodo, kakegoe no narai (時のそうどう懸けごえの習い) (the skill of shouting and causing distraction) used to escape "final discovery". Claiming there's a fight going on when there really isn't is a good example of this. Another way of escaping is by preparing a hole through a hedge by using a tub with it's bottom cut out. A shinobi would push the cylinder onto the hedge to create an opening for later use.
To gain information on someone's financial situation a shinobi could offer the person an expensive item for a cheap price. If the target doesn't have enough money he will not buy the item, if he can afford to get a loan he will. By observing the way he reacts a shinobi could know exactly how much money a person has. To counter the same trick, students would tell the seller that they have an acquaintance who wants the item as to not reveal any financial information.