|Spoiler Alert: This page contains spoilers. Read at your own risk.|
Ghost Walker (鬼門 遁甲) is a Mental Interference Type Magic of the Outer-Systematic Type. It is an Ancient Magic that manipulates the vectors. Based on the user's wishes, this secretive magic can redirect other people's attention to the desired location and people with their vectors scrambled will never locate their target. Much like someone who intends to walk straight forward but is actually walking in circles, or maybe seeing a carriage plainly in walking distance but is never able to catch up. 
Ghost Walker was a magic that selected position based on fortune and is unrestricted by physical parameter consciously manipulating the target directions is the basic of Ghost Walker.
This magic is also called Kimon Tonkou or Kimon Tonkouno-jutsu. Kudou Minoru describes it as follows:"It is a magic art from the continent, the art of Kimon Tonkou, in essence is Spirit Interference Magic that derails orientation."