Fukōken

Fukōken (巫後見, "Shamanic Guardian") are guardian spirits that accompany Shamans and enhance their Fujutsu. The relationship with their Guardian Spirit is the most important source of power for any Shaman. A perfect unity between a Shaman and their Guardian is what results in a true Fujutsushiki.

Overview
A Fukōken can be any wandering Spirit a Shaman chooses to be their partner. A Spirit's power is separate from that of their master, and when a Shaman draws on this power in addition to their own, their Fukōken will become even stronger.

Fukōken can be someone the Shaman knew when they were still alive, they can be an animal spirit or even a diety. Each different kind of Spirit brings its owns strengths, which is why its important for a Shaman to pick a Spirit they're compatible with. Doing so is the first true step to becoming a Shaman.

Abilities & Powers
Ghost Physiology: Like any other Spirit, Fukōken cannot be perceived by normal humans. They can move through walls and the ground at will, unlike their human partners. They are also incapable of being contacted without the use of Furyoku, making conventional means of harming them impossible. Fukōken who have been injured can be restored using their Shaman's Furyoku.

High Furyoku Levels: The longer a being has existed, the more memories and experience they've accumulated. Once they pass on to the Hidden World after death, all of this becomes Furyoku. While Spirits are primarily unable to tap into their Furyoku through Fujutsu, Shamans can do so at will. This allows Shamans to effectively square their own Furyoku levels, generating much more power for advanced Fujutsu.

Fujutsushiki
Fuhyōi (巫憑依, "Shamanic Possession"): A technique that willingly allows a Fukōken to possess their Shaman's body. This allows the Shaman to utilize their Fukōken's abilities for themselves at the cost of their own Furyoku. Mastering Fuhyōi is the first step to developing a Fujutsushiki.

Fujutsushiki (巫術式, "Shamanic Techniques"): Fujutsu that creates metaphysical construct by fashioning an a Fukōken to a Fugu in order to manifest supernatural abilities. Fukōken can only take physical shape through a body Furyoku, and a Shaman can only draw out the full power of their Furyoku by utilizing their Fukōken. There are three types of Fujutsushiki: Weapon-type, Armor-type, or Summon-type.