Among the less common threats to humans are ghosts and spirits. While ghosts are a fairly common occurrence (especially around Karasumori), they seem to rarely become threats, and are typically not treated as such unless they prove aggressive toward humans. Spirits are more elusive, especially from a Kekkaishi standpoint, but this is likely because spirits are the natural enemies of exorcists, just as Ayakashi are the expected enemies of Kekkaishi.