A psychic ninja fantasy suggesting that the assassins did not die out during the Sengoku era but burrowed under Japan, where they fought a new war against the alien occupants of a crashed spaceship that has lain undisturbed for several millennia. (Source: The Anime Encyclopedia)

Powerful, avaricious sorceress Lina Inverse travels around the world, stealing treasures from bandits who cross her path. Her latest victims, a band of thieves, wait in ambush in a forest, thirsting for revenge. When Lina is about to effortlessly pummel her would-be attackers, the swordsman Gourry Gabriev suddenly announces his presence. Assuming Lina to be a damsel in distress, the foolish yet magnanimous man confronts the brigands in order to rescue her. After defeating them posthaste, the oblivious cavalier decides to escort Lina to Atlas City. Though not very keen on this idea, she ends up accepting his offer. However, without realizing it, Lina has chanced upon a mighty magical item among her most recent spoils. Now two mysterious men are hunting the young magician and her self-proclaimed guardian to obtain this powerful object for apparently nefarious purposes. This way they begin their adventure, one where the fate of the world itself may be at stake.

In the kingdom of Xoana, Lina Inverse and Gourry Gabriev unexpectedly come across their old companions, Zelgadis Graywords and Princess Ameilia Wil Tesla Saillune. Upon their reunion, the friends end up easily foiling the King of Xoana and his daughter's dastardly plans of world conquest. Soon after, it is revealed that Zelgadis is in search of the world's most valuable magical tome, the Claire Bible, hoping to discover a method to recover his human body among the many secrets sheltered within it. Despite his protests, the rest of the group decides to join in the quest after hearing of his mission. However, just when they were wondering where to start looking for the legendary book, they stumble upon a mysterious priest by the name of Xellos, who claims that he may be of some help in their pursuit.

In the city of Kouchi, high school student Taku Morisaki is going about his work when his friend Yutaka Matsuno calls and asks him to get to their school as soon as possible. Taku arrives, and Matsuno introduces him to Rikako Muto, a beautiful girl from Tokyo who recently transferred to their school. Although Rikako is academically and athletically gifted, her generally unpleasant attitude leaves her with virtually no friends outside of Matsuno and another girl from her class. After a chance encounter during their class trip, Taku suddenly finds himself more involved in Rikako's personal life, much to Matsuno's dismay. Struggling to balance his friendship with Matsuno and his own budding infatuation for Rikako, Taku must come to terms with his feelings and understand how a girl with a troubled past is having such a massive effect on his life.