Mahou Senshi Sweet Knights: Heroine Ryoujoku Shirei

An evil syndicate leader from a far planet wants to rule his nemesis kingdom and his mission consists of gaining the trust of the Sweet Knights, the two japanese girls bestowed by Queen Gloria with the power to protect the surface world from the monsters of the syndicate. After discovering their weak points, Metzer will use his monsters to defeat, kidnap and brainwash the Sweet Knights into sex slaves devoted to Zerou's cause.