Leviathan (Light Novel)

is a light novel side story written by Eiji Otsuka, with illustrations by Yu Kinutani. The series began publication on January 10, 2004 by ASCII Media Works under their Dengeki Bunko publishing imprint.

Synopsis
After a long absence, the young shaman Samizo Kohei returns from the dead with a prophecy of the apocalypse. Or part of him returns, at least - most of his body has been replaced with the transplanted body parts of his former friends, all retaining their distinctive personalities. He returns to his home in Shinjuku, where he works as a psychic surgeon in an unlicensed clinic. Here he serves as the unofficial guardian of the Shinjuku underground, solving paranormal murder mysteries, with the assistance of an assortment of other bizarre mystics and semi-human allies. Meanwhile, the others wonder exactly what Kohei has become, and whether he has returned to prevent the apocalypse, or to initiate it.

(Original Manga Synopsis)