One of the charming aspects about animé is the peculiar kind of logic they adopt. The most outrageous cosmic events are introduced merely to serve tiny character quirks.

In the first installment of this new serial, a female alien comes to Earth (via the technology of a starship) to elicit the help of a mere teenage boy in her quest to defeat a rival race! Once established, that plot is punted aside to reveal the real story: how the alien girl wants to have sex with a human - which she does, with remarkable frequency. She also wants him to call her "little sister," adding an incestuous angle (as if the alien/human angle isn't enough). It's all outrageously campy and sexy to boot.