Senjutsu is a variation of Focus Essence, giving its users the power to harness their Essence (more commonly refereed to as Chi) into a flow or current, offering them control over it.
Senjutsu is different from magic and sorcery. The biggest difference is that Senjutsu stresses the importance of something called Chi or Chakra, the energy that flows from one's spirit into their body, in other words, one's life-force, and turns it into a constant current.
It is a power that is both similar yet different from the magic of Dragons and the light power of Angels. Its direct destructive power cannot match that of magic or the power of light, but Senjutsu can make use of the unknown part hidden within plants, animals, and people. For example, if one learned Senjutsu, it is said that they could excel at reading the flow of someone's spirit, of their aura, and that they can also grasp the movements of a faraway target to a certain degree.
Senjutsu, however, also possesses a fatal flaw. While Senjutsu allows the user to read and handle spirit energy, it also takes in the malice and ill will that floats in the world, therefore should an amateur use it inappropriately, the malice will corrupt the user.
Unlike Focus Essence, which mainly relies on creating powerful blasts of power, users of Senjutsu control the flow of Chi, strengthening their physical bodies or causeing vegetation around them to bloom or to wither. Knowing Senjutsu allows the reading of Chi and auras and to spy on the target's state from afar. Disrupting the opponent's Chi or severing it can cause direct damage to living things. There are very few ways to defend against Senjutsu, one of them being the use of Focus Essence to create a barrier. Though even this does not guarantees complete protection.
Amina has stated that Bouchujutsu, a.k.a. the Bedroom Method, a.k.a. "having sex", is the best way to utilize Senjutsu's healing properties.
Similar to Focus Essence, the most basic way of learning Senjutsu is through meditation. Concentrating on their state of mind, to quietly release their own Chi as well as sensing the natural Chi of their surroundings is also the best way to develop one's skill in Senjutsu.
To use Senjutsu, the users commonly concentrate their Essence around the hand and use it to attack the opponent. The method to attack using Senjutsu may be in the form of hand-to-hand combat or blasting the power towards the opponent.
One of the main differences between "classic" Focus Essence and Senjutsu is that, while the former relies more on the projection of energy, the latter in more "physical".