Star Of David: Beauty Hunting (1979)

aka’s: Debido No Hoshi: Bishoujo Gari/Beautiful Girl Hunter/
堕靡泥の星 美少女狩り

At the age of 18, an apparently normal boy (Shun Domon), conceived through rape, suddenly turns into a raving sex-fiend. He lures beautiful girls into a self-constructed torture chamber to abuse them and then finally kill them. The horror reaches a climax when the boy teams up with his rapist father (Shôhei Yamamoto). Now father and son both unleash their perversions on the captured girls. (In Japanese language, with English subtitles).