Wild Adapter, book 4
Kazuya Minekura2003

Kubota Makoto led a somewhat easy going life, until a local yakuza boss approached him for initiation, and he happened upon a 'stray' in an alley, Tokitoh Minoru to be exact, whose life seems to be forever connected with a drug, W.A., passing frequently through the Yokohama area, and leaving bodies in it's wake. As they further investigate the drug, more information than perhaps wanted is brought to light.