Charms are usually objects that are worn to ward off evil or ensure good fortune. All Japanese war arts have an element of ritual magic. For the shinobi and samurai, magic can be divine and given from the gods.
The Shoninki shinobi manual included a charm used for protection. It created by cutting some rough and heavy straw magusogami paper into about a 21 cm square, writing a spell on it, and pasting it in the corner of the room the shinobi sleeps in, in a southeast direction called tatsumi. It should be blessed by performing cold water bathing and fasting, and then it would be carried around.
Another charm included is used to make people stick together or split up. The date will be written on the top left of the paper with the name of the user on the bottom, second to the left. The target's name would be written on the bottom left with the spell on the right, down the page from top to bottom.
When the shinobi chants the names of the targets, he would fold the paper to have the two names over lap perfectly in order to be on good terms. To create an argument between the two people the paper will be folded without having the two names overlap.
The same charm could be kept in the folds of a shinobi's kimono in order to have better encounters with the target or create discord between the enemy and his retainers. The spell could also be used to fix marriages.