The Dunbas Empire has set their sights on conquering the tranquil land of Rimbell, but the three princesses are determined to fight back. Luna, in particular, stands out for her tomboy ways and impressive swordsmanship. When she embarks on a magical adventure in the castle cellars, she unexpectedly finds herself inhabiting the mind of Varga, a legendary green reptile, and even gains a reptilian tail in her human form. Now tasked with defending her kingdom against a relentless giant invader and rescuing her sister, who was taken by a pterodactyl, Luna faces an enormous challenge.