Kyōgoku's ability allows him to give someone a 'possession' from the sky and the target becomes mentally ill according to the possession (a random yōkai) that falls on them. Since yōkai are chosen at random, they can be hit or miss, and in the case of a miss, a "pickle" will fall on the target.
Moreover, his "spirit possession" can't deal with physical damage. 
The ability is related on the occupation of Akihiko Chuzenji, one of tha main characters in Kyōgōkudō', whose occupation is a shaman priest and solves a case using exorcism. Kyōgōkudō is a famous novel work by Natsuhiko Kyogoku. It is a series of mystery novels.