Twilight of the Dark Master (manga)

The year is 2019, and Shinjuku's drug trade just got a whole lot bloodier. A new narcotic endows users with demon-like horns, fangs and a raging appetite for human flesh. When a man named Eiji Kuraza transforms into a murderous demon and then goes missing, his girlfriend Shizuka will stop at nothing to find him.

Following a trail of violence, narcotics and prostitution to the yakuza, Shizuka hires supernatural P.I. Tsunami for his expert legwork while Shizuka joins the red light district to conduct her own investigation on her back. If Shizuka's recklessness pays off, Eiji may force her to satisfy an appetite unfamiliar to call-girls...