The Dunbas Empire tries to conquer the peaceful land of Rimbell. The three princesses are determined to resist the invaders, expecially the middle one, the tomboyish, sword-wielding Luna. After a magical escapade in the cellars of the castle, she finds herself embedded up to the hips in the head of a huge green reptile, the legendary Varga, and acting as its "brain". Even when in human form she has a reptilian tail. She has to fend off a very persistent giant invader and rescue her sister who has been kidnapped by a pterodactyl.
(Source: AniDB)
— Description from AniList community (anilist.co).
