Spiritual Surgery is the ability to selectively phase only certain parts of the body, while still holding oneself completely together. User makes their hands phase through matter and can perform surgeries on people without touching their skin. This allows them to speed up the body's natural healing process by transfering their ki directly into them. It can be used to treat both external and internal injuries. The strength of the technique is directly proportional to the ability to utilize their own ki. I.E a person who can manipulate the elements can perform this technique significantly better then someone who can only harden their hands to crush stones. The fact that all of this is done while utilizing a refined version of phasing means that, only a few highly skilled individuals are able to use this technique. User also gains direct access the pathways of chi in the human body allowing them to manipulate its flow curing or increasing the effects both physical and spiritual in nature, such as curses, pressure points, ect. Saisei used this to manipulate Shinrei water dragon inside Yuya's body.
This technique can also be used phase parts of whatever user is touching. For example, user could cause an opponent to phase, while keeping their weapons solid so that the weapon falls through opponent's hands. It can also be performed offensively. By sending an excess amount of energy into the patient's body, the user can overload the patient's normal circulation, trapping them in a comatose state. User could also pass a part their body within another living being and ever so slightly exit decrease their phase state.Even a minimal shift is sufficient to cause the organism they pass through excruciating pain, a shock to the nervous system, and unconsciousness. Were they to deshift any more the shock would probably kill the other organism.