The Rapeman 4(1994)

Original title: ＴＨＥ　レイプマン４

A senator's secretary seeks out Rapeman's services to rape his fiancé who has been brainwashed by a local cult. According to the by-laws of the cult - if the woman has sex with a non-member, then she will be disassociated from the cult, thus bringing the wife back to her husband. This back-fires when the cult does not ex-communicate her - so Keisuke and Uncle infiltrate the cult to get to the bottom of their shady dealings. The resulting investigation embroils the duo in a conspiracy between the cult and a sleazy politician that can only be "righted through penetration"...