Rage of a Ninja (1988)

"Once they were brothers in the same Golden Circle but their lives followed different paths. There is a ruthless assassin on the police connect a series of violent jewel thefts to him. But, unbeknownst to the police, the thefts are the work of an organised gang dedicated to finding the ancient secrets and power of the Golden Circle.
Their leader was once one of the fabled brothers but, he is now intent on evil, power
and corruption. He must be stopped at all costs" - VHS back of the box description. Hong Kong cut and paste edit of the 1986 Taiwanese Adult film "午夜激情" (Midnight Passion) with new ninja scenes.