A Shadow (影法師 Shadō) is the materialization of one's spiritual power into a shilhouette representing the user. As the manifestation of one's spiritual power, a Shadow is usually as powerful as the user, but any damage it receives will also be done to the user, and its destruction results in the user's death. It can be used to increase the user's spiritual powers through special dangerous training, which Reiko Mikami did with Shōryūki.
Mikami's Shadow has the shape of a female warrior. After her training the Shadow's armor and weapon were enhanced. Mikami is able to control her Shadow without problems, but the Nightmare managed to take control over her Shadow when he hijacked Mikami's body.
Shōryūki is able to transform into her own Shadow.