A spell or charm is a set of rituals which are meant to invoke a magical effect.
The Shoninki shinobi manual included a spell used for protection. It involves cutting some rough and heavy straw magusogami paper into about 21 cm square, writing the 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 carrying it around as a charm.
Another spell included is used to make people stick together or split up. The date will be written on the top left 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.