Hiden

Hiden (秘伝; Literally meaning "secret tradition") are techniques that are kept secret by a group of people, usually a clan. They are kept extremely secret, passed orally in order to stop others from learning how to use the technique. This is done to help ensure that no outsiders to the group learn of the technique, for various reasons. Hiden are often mistaken with Kekkei Genkai techniques - the difference being that the latter are unique to a group because it uses an ablility passed down genetically. However, Hiden used by a clan often use a certain tool or ability in all their techniques, making it seem as if they are Kekkei Genkai.