Yōkai (Kai)

Yōkai (妖怪, Phantom) also known as Ayakashi (妖) entities composed of pure spiritual energy which reside in the Spirit World (異界,Ikai).

Overview
Yōkai are known to be entities of pure spiritual energy and reside in the Spiritual World. Due to being composed of spiritual energy, they are unable to exist in the without outside help. However, especially strong Yōkai can bypass this. Yōkai are divided into two different classes and four types.