Koroshiya 1 (2001)

The movie centers around Kakihara, a sadomasochistic enforcer seeking his missing boss. Along his quest, he encounters Ichi, a repressed and psychotic killer. Kakihara sees in Ichi the potential to inflict extreme pain. The story revolves around the psychological damage inflicted on a man manipulated into violence, engaged in attacking or even killing members of feuding Yakuza gangs, while he's pursued by a sadomasochistic enforcer.