Ningen kyôki: Ai to ikari no ringu (1992)

The Karate Kid is forced to fight in the underground fight-club for a privileged few wealthy sadists who enjoy watching catch-weight death-fights between men and women from different martial-arts schools. His principles forbade him to fight such matches, so the promoter forces him to watch his girlfriend being stripped and finished by a stronger woman, and then a young mother badly in need of money, entering a couple of matches. She survives two matches surprising the promoter, who arranges for a mixed tag match which end he has carefully arranged for.