Count Walter Delamare travels to Japan to find a cure for his lycantrophy. He meets a scientist named Kenji Onishi, who agrees to help him, and also introduces Walter to his daughter, Wendy Onishi. Wendy is instantly drawn to Walter, who returns the interest.
One day, Wendy offers to take Walter on a sight-seeing tour of Tokyo, during which they run afoul of a brutal mafia. The boss, Toshida, puts out a bounty on the head of Walter. A gang of ninja mercenaries take him up on the offer and set out to hunt Walter down.
One night, Wendy pursuades Walter to take her virginity. While they are together, the ninjas break into the lab and interrogate Onishi, who refuses to give up Walter's whereabouts. They then murder him and burn his lab, but not before stealing some his research into Walter's DNA.
When Walter and Wendy learn of this, Walter is enraged and decides to kill the mercenaries, who have already delivered Walter's DNA to Toshida. After a brutal showdown, Walter kills every member of the group, avenging his friend.
Walter and Wendy decide to escape Japan on a fishing trawler, unaware that the trawler is owned by Toshida, who uses it for drugs shipping. When he realises Walter is on board, Toshida takes over the boat. As Walter turns into a werewolf and begins slaughtering Toshida's men, Toshida injects himself with the DNA and becomes a werewolf. He tries to kill Wendy, but Walter retaliates and tackles him over the edge. Wendy watches in horror as both of them disappear into the ocean. At the very end of the film, however, Walter is revealed to be alive.
The film was followed by Shadow of the Wolfman.