Ordinary fourth-grade schoolgirl Sasami Kawai's life takes a dramatic change of direction when she meets Tsunami, the newly-appointed queen of the magical kingdom of Juraihelm, who appoints her as a representative of good on Earth. Sasami becomes the magical girl Pretty Sammy. However, Ramia, rival for the crown of Juraihelm, plans to scupper Tsunami's bid for leadership by pitting Sammy against her own creation, Pixy Misa.

International businessman and computer billionaire Bif Standard,whose "SynchroniCity" operating system runs on 95% of the world's computers, makes a bid to conquer the Japanese market. When Ramia hears of his plans for world domination, she steps in to help Bif achieve his dream with her magic. Trouble is afoot for the Kawai family when Tenchi tries to buy software for their computer and gets the only remaining copy of a non-Standard operating system...

After a comet strikes Japan, Ramia mysteriously goes missing, and Sasami's life seems to have returned to some semblance of normality. A week after the impact, the Kawai family take a trip to the beach resort near the site, but the town is attacked by a mysterious man who has taken over Ramia's task of dethroning Tsunami. Meanwhile, Washu investigates a strange extraterrestrial life form that was found at the crash site.