All parts of the series are about Tenchi Masaki adolescents. This freed by mistake a demon who was imprisoned several hundred years ago by one of his ancestors in a cave. This turns out to be as Space pirates and descendant of a prince from another solar system.
Gradually, more female aliens come to want to seduce a space police officer, two princesses (and young sisters of the grandfather) and a scientist (who is also the mother of the pirate), the Tenchi, and use him for their own purposes.
