Thomas Hoshino is a tough Japanese detective, who lost his partner by a deadly Yakuza killer Jaho. He tracks down the killer and his master to Los Angeles, where he teams up with Det. Karen Ryder. Soon they discover that Jaho is preparing a gang war and weapon smuggling ring. Hoshino must find a way to defeat the killer who posses mystical ninja powers.

When Nick Davis leaves prison after one year in solitairy, he is hired to operate a forklift in a warehouse in the harbor owned by the Japanese Yakuza patriarch Isshin Tendo. The place is assaulted by the Italian Mafia lead by Dino Campanela and Nick rescues and saves the life of Shuji Sawamoto, who is the representative of Yakuza interests in America. Shuji hires Nick to work for Yakuza and becomes his godfather in the family after his oath to join Yakuza. However, Nick is a lonely FBI undercover agent assigned to penetrate the criminal organization. When the FBI discovers that Campanela is organizing a massive attack to destroy the Yakuza, Nick's boss Littman calls off the operation to leave the dirty work to the Italian Mafia. But the connection of Nick with Shuji and his goddaughter Yuko forces him to help his Japanese family.

As sadomasochistic yakuza enforcer Kakihara searches for his missing boss he comes across Ichi, a repressed and psychotic killer who may be able to inflict levels of pain that Kakihara has only dreamed of.