There are various things in ninjutsu that deal with internal energy and such. The most commonly referred to form of this is the kuji kiri. These are the famous mantras and such that allow a ninja to focus his energy through various mental states and for different purposes. For example, controlling nature, reading someone's mind, etc. Granted, such could and would probably not be taught, yet alone understood, until one has had many years of training and is of a high ranking status (usually). I know I could never handle the kuji at the level I am at right now. I'm a long ways off, at best.
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