A Purification Circle (祓円, Haien, lit. "Exorcism Circle") is the energy field in which an exorcism takes place. It erects a barrier between the subjects and their environment to prevent interference. It opens the Gates of the Three Worlds, where the Soul is then sent to Heaven or Hell.
There are several ways to cast a Circle. The first way involves using the Athamé to focus one's spiritual energy into a circle. It can also be done without an Athame as a form of Kūdō, usually by clapping one's hands and then putting one's palms to the ground, which creates the same column of energy that contains the demon.
- Celestials - No Purification Circle is actually drawn out; it automatically appears around the Angel as a field of energy. They move first with the Athamé, severing the Tsukigami's connection with their host. The Tsukigami is cast into Hell or elsewhere in the Realm, according to Ten'i, and the Shigyoku and Host fall free.
- Espers -
- Vespers - The Purification Circle is drawn by the Athame or through a Kūdō rite, or summoned from a Seal. The Athamé severs the connection between the Tsukigami and host and destroys the Tsukigami along with its Shigyoku. If the Shigyoku remains, it is usually brought back to the Agency for research purposes.
After the exorcism, the Circle fades, and all that is left is usually the Shigyoku and, if applicable, the unconscious host. If the spirits contained within the field are too powerful, they may break the circle.
A successful exorcism takes place in a Circle that can filter out outside energy. The force field effect prevents any spirit energy from leaking in or out, protecting both the host and the outside world.