The series begins with a raid on a group of bandits at the hands of the 15-year-old sorceress Lina Inverse. On her way to Atlas City, she is surrounded by bandits. Just as Lina prepares to attack, a mercenary swordsman, Gourry Gabriev, appears and defeats the bandits. Lina and Gourry befriend each other. Soon after, Lina and Gourry are asked to exterminate the dragon threatening a small village. Having no reason to refuse, Lina takes on the job despite Gourry's dissuasion. Being intimidated by the dragon, Lina is outraged. Lina uses the Dragu Slave technique on the dragon, killing it and destroying most of the village. Lina and Gourry eventually run away from the villagers after the village's destruction.

Lina and Gourry go to a magic shop in town to sell the treasures that Lina snatched from the bandits. However an item from the booty, a knife, is cursed and it turns the shopkeeper violent and a hullabaloo starts. Lina and Gourry fight a hard battle but the chaos is brought to a sudden stop by a single bark of the shopkeeper's wife. While they are relieved, a mummy called Zolf, attacks our heroes with the evil trolls. He is looking for one of the items Lina possesses. Lina and Gourry are fighting their way out. However, on the same evening, Zolf shows up to their room again with a mysterious person.

The mysterious person says that his name is Zelgadis Greywords. He is a mixture of human, golem and demon; a creation of utter evil. He offers to buy Lina's booty, but Lina asks for an outrageous price which drives him away. Not giving up, Zelgadis comes back to take Lina's booty by force. Lina is hurt and thrown into a pinch. Luckily she is saved by the legendary great sage, Rezo the Red Priest. Rezo warns Lina that Zelgadis wants to resurrect the mazoku Shabranigdo, the demon king, then Rezo mysteriously disappears after performing some unknown spell...

Lina and Gourry start investigating a way to stop Shabranigdo's resurrection, however they are plagued with a question. Why is Zelgadis trying to revive the Demon Lord? On the other hand, Rezo cannot easily be trusted. The situation becomes more complicated when Zelgadis and Zolf realize that they are no longer able to scry for the as yet unknown item that is in Lina's possession. While our heroes are traveling through a forest, Lina informs Gourry that she will not be able use her sorcery effectively for a few days. This makes her vulnerable to any villains that may challenge her. As fate would have it, Zelgadis and his men come to attack. During the exchange, one of Zelgadis's men, Dilgear the Werewolf/Troll, lets slip that it is, in fact, the Orihalcon statue that has them chasing Lina across the countryside. Lina narrowly escapes the initial attack and is separated from Gourry. However, she is quickly ambushed, knocked unconscious with a spell, and captured by Zelgadis.

Lina awakens to find that she is held captive in Zelgadis' hideout. After Lina is questioned about the Orihalcon statue, she lies about why Zolf is unable to locate it magically. She is then asked why she didn't fight back harder in the previous skirmish. Zelgadis determines that she should be kept alive until they retrieve the statue in any case and she is then subjected to threats of torture by Zolf and repercussions for her previous treatment of him, much of it ineffective, to his dismay.

Rezo suddenly appears during Lina's escape of and calls Zelgadis a traitor. Lina is surprised to discover the relationship between the two. Zelgadis' grudge against Rezo makes him revolt against him. Lina and Zelgadis barely make it out virtually unharmed, with Zelgadis using Lina as a distraction against Rezo, with quite a bit of protest from Lina. Rezo's men discover the escape, as well as the cooked Noonsa, and subsequently eat him, all while swearing vengeance for his death. Soon after escaping Rezo, Lina and Zelgadis take a break to rest and Lina, being quite confused after find out about Rezo and Zelgadis's relationship, asks Zelgadis to explain to her just what, exactly, is going on.

Under the villains' ceaseless attack, Lina and Zelgadis have no time to rest. Meanwhile, Rezo begins to summon the demons in order to capture them. Outnumbered by the enemies, Lina and Zelgadis get into a pinch. Suddenly a shining knight pops up. It's Gourry who has been looking for Lina. He draws his ancestral sword, the Sword of Light, and slashes the fiends. Zolf and Rodimus, two loyal followers of Zelgadis, come to help them, our heroes shake off Rezo and his band.

While taking a rest in a village, Gourry and Zelgadis start fighting over the Philosopher's Stone. Lina calms them down but they become more hostile with each other. Then, they receive a message from Rezo, stating that unless they give the Philosopher's Stone to him, he will turn all the villagers into stones. Having no choice, Lina and the others go to meet Rezo. Lina has no intention of giving the Stone to Rezo because she knows that the Red Priest is scheming to resurrect Shabranigdo. Rezo manages to hypnotize Zelgadis and makes him steal the Stone. With the Stone in his possession Rezo revives the Dark Lord Shabranigdo.

Rezo succeeds in resurrecting the Dark Lord, Shabranigdo. However, Rezo's body is taken over by the Dark Lord which was not part of his plan. Zolf and Rodimas recklessly challenge Shabranigdo, but are no match to the power of the Dark Lord. All Lina and others can do is to run from the ferocious demon. Shabranigdo's evil power spreads out to the surrounding areas. The weather turns abnormal and monsters become wild. Seeing the monsters attack the village, Lina and others decide to fight back.

Lina and the others challenge the Dark Lord, Shabranigdo. Unfortunately, he is too powerful and no magic works against him. Gourry is knocked down and Zelgadis is struck hard. Then, Lina is given the Sword of Light and it increases the power of her sorcery. Lina challenges Shabranigdo with the most powerful incantation, Giga Slave, which is superior to the Dragu Slave. She realizes that Rezo is still inside Shabranigdo. In the final moment, Rezo gets away from the body of Shabranigdo and finally Lina's Giga Slave smashes the Dark Lord. Upon arriving in Atlas City, Zelgadis decides to part ways with Lina and Gourry.

After destroying Shabranigdo, Lina and Gourry continue their journey. They hear a rumor about the first successor to the throne, the prince of Seyruun Kingdom. Lina dreams of marrying a wealthy young man, but the prince turns out to be a forty-something scruffy-looking man. Phil, the prince, offers a bodyguard job to a disappointed Lina. Lina reluctantly accepts the offer. Then Randy, who is the third successor to the throne, appears with his loyal subordinate, Brassdamon. Randy has a plot to kill Prince Philionel. Lina meets Amelia, Phil's daughter, who is a self-proclaimed Lady of Justice. Amelia punishes Randy for treason by slashing Randy with the help of her father. Lina can't help but to wonder why they hired Lina as a bodyguard in the first place.

Lina's Dragu Slave spell works tremendously well on bandits. Impressed, Amelia insists on learning Lina's sorcery. However, Lina is concerned by Amelia's reckless ways and orders hard training for Amelia, instead. However, the training has little to do with actual sorcery. Impressed by Amelia's enthusiasm, Phil asks Lina to show his daughter the Dragu Slave. Lina's incantation breaks the seal of ghosts and throws the Kingdom into a chaos. Lina is not well versed in white magic and fights a tough battle with the ghosts. Just when they think the Kingdom is going to be destroyed, Amelia saves it with her white magic. Amelia finally understands that she doesn't have to practice a powerful incantation.

Lina, Gourry and Amelia finally arrive in Seyruun and see the wanted poster. To their surprise Lina and Gourry find themselves on the wanted poster. Amelia, the Lady of Justice captures them, stating that she just carries out her holy mission. Lina and Gourry are handed over to two bounty hunters, Zangulus and Vrumugun. After sealing Lina's magic and taking away Gourry's swords they are both placed in jail. But Lina and Gourry somehow manage to escape. Outraged Lina and Gourry challenge the bounty hunters. They are cornered by strong counter-attack of Zangulus and Vrumagun. Amelia, dismayed in judging who is good and who is not, manipulates a strong incantation, saying "whoever stays alive is good!" and blows up the entire area. Lina and Gourry barely survive it, and continue their journey to Sairaag where they are told the person responsible for the wanted poster can be found.

Lina and her friends are still pursued by the bounty hunters. They try to lose them in the mountains to no avail. Our heroes have no time for a meal and their empty stomachs is taking a toll on them. They follow their noses into a cave where the smell of delicious food emanates. But it is a trap setup by Zangulus and Vrumugan... They narrowly escape from the cave and escape on a raft in a rapid stream. Zangulus and Vrumugan try to catch on, but finally Lina's magic knocks them out and the pursuers are thrown into the water.

On their way to Sairaag, Lina and her friends meet a young boy named Harris. He asks Lina to be his bride in a fake marriage because he's been forced by a witch, named Callie, to marry her daughter. Lina reluctantly accepts his request and attends a fake wedding ceremony with Harris, but then Zangulus and Vrumugan jump in. The ceremony is in a chaos and Lina has to fight in her wedding dress. While Callie and Vrumugan fight against each other, Lina recites an incantation and wins the battle. By accident Lina blows up Harris' house in the battle and as a result doesn't receive her fee from Harris.

In exchange for food and transportation, Lina's team joins a traveling theater company managed by an eccentric director and is heading near Sairaag for a competition. Ironically, the play they perform is "The Death of the Abominable Fiend Lina Inverse" and revolves the hero defeating a fictional, evil Lina Inverse. Amelia is cast as the protagonist and falls in love with the role's frequent proclamations of justice. During the competition, Zangulus and Vrumugun launch an attack on the play, which the audience mistakenly believes is part of the show. After Lina and friends defeat the enemy, the audience and judges award the team 1st place, praising the unpredictable plot, marvelous special effects, realistic combat.

Lina, Gourry, and Amelia are getting closer to Sairaag. In order to outrun the tenacious pursuers they try to board a ship, however the ship is also watched by the bounty hunters. Gourry dresses up in women's clothing and our heroes boards the ship as sisters. On the ship, Volun, a self-professed "Braveheart", proposes to Gourry. Gourry freaks out while Lina and Amelia laugh hysterically. All of a sudden a dragon roaming the area attacks the ship which is then forced to return to the harbor. Lina fights a fierce battle with the dragon and finally defeats it, leaving the legend of "the Celestial Maiden who saves folks" behind. The next day when Lina and her friends board the ship, Volun shows up yet again. Gourry is no longer in disguise, however Volun does not care and persistently comes on to him...!

Our heroes finally reach Sairaag. They sneak into the town under the darkness of the night and rest in the house of Sylphiel, who is one of Gourry's friends. While at the house they find out about the person who may be responsible for placing Gourry and Lina on the wanted posters. They break into the hideout of the culprit only to be ambushed by Zangulus and Vrumugun as well as one more villain, Eris, their boss. Lina slashes Vrumugun, but then she faces a man who is identical to Vrumugun. Vrumugun's true self turns out to be a clone created by Eris. When Lina is cornered by another Vrumugun, Zelgadis gallantly saves her. Is the tide turning in favor of our heroes? No, not yet. A man appears in front of them. It is Rezo. How could this be?!

Lina and her friends are shocked to see Rezo alive, standing right in front of them. At the same time, they suspect that Rezo may be a clone just like Vrumugun. They visit the Sorcery Church in order to find out more information about the clones, but discover nothing. Rezo appears again and attacks them with as much power as he used to have in their previous encounter. The Red Priest tries to take the Sword of Light from Gourry and while our heroes struggle to escape, the entire town is engulfed in fire by Rezo's powerful incantation!

Reciting numerous incantations for self-defense, Lina and her friends manage to defend Rezo's fierce attack. Rezo's powerful black magic destroys half of the town, yet our heroes manage to escape. They must find a way to destroy Rezo. They head for the institute where Rezo used to experiment with his magic. Rezo is still not fully recovered and needs rest. He sends Rahanimu, a monster that is half-human and half-fish, to stop our heroes. Lina and her friends battle with Rahanim who is accompanied by Zangulus. Zelgadis uses his smarts to defeat Rahanimu and our heroes get out of a pinch. They finally reach Rezo's institute.

Lina, Gourry, Amelia and Sylphiel get to Rezo's museum. They break the seal by the Sword of Light and look for Rezo's secret in the underground chamber. They are caught in a trap set by Eris and become separated. While Lina searches for Gourry and Amelia, Sylphiel asks her about her relationship with Gourry. She tries not to show any feelings for Gourry other than a mere friendship. In the meantime, Gourry is in the middle of man-to-man battle with Zangulus. He is cornered by the strong opponent but Gourry uses the full force of his Sword of Light and defeats Zangulus.

Lina and her friends rush to the lowest level of Rezo's institute. Tiva, the demon who has been guarding the institute gets in their way. Tiva is easily beaten by Lina as his magic was sealed by Rezo. Tiva guides our heroes to the lowest level and they break the last seal to enter the laboratory. The laboratory is filled with junk and as they look for Rezo's secret they have no clue what's what. Tiva pulls out a mask which allows him to unseal his magic power. Tiva then regains his power and attacks Lina and her friends. Tiva's evil magic is too powerful to destroy but our heroes manage to find a copy of the Claire Bible. All of Rezo's secrets are written in this book and they manage to crush Tiva.

Rezo's secret is revealed in the book found in his institute. However it is too early to celebrate as Rezo and Eris storm into the institute. Rezo has great power and Lina discovers that this Rezo is a clone controlled by a device on his forehead. Eris is also very tough. Two fiends take the book of secrets back and in a split second attach the control device on Gourry. While Lina and Amelia are busy holding down Gourry, Rezo and Eris break Rezo's seal and create Zanaffer, a demonic beast. Eris is excited to find Rezo's inheritance. Then, the clone Rezo attacks Eris. When the clone is out of Eris's control, it is awakened to his self-conscious and resists the master.

Relieved from Eris's control, the clone Rezo assaults Lina and her friends with his own will. The clone gets the power of Zanaffer, the demonic beast, and wants to prove his new strength. He challenges Lina's Giga Slave. Lina is almost provoked into using this powerful magic until Sylphiel stops her. It may destroy the world if it gets out of control. The clone attacks Sylphiel and Lina shields her taking the clone's tremendous blow.

Having been struck by the clone Rezo Lina is injured. Her friends try to help Lina escape, but even the power of Sword of Light doesn't work against the clone. Prince Philionel, Amelia's father, jumps in to help them out but he is no match for the clone Rezo. Our heroes escape into the basement of the Sacred Tree, where Lina has already entered before them. Lina is completely healed thanks to Sylphiel's cure incantation and the power of the Blessed Blade that is found there. She once again faces the clone Rezo with the Blessed Blade in her hand.

In order to have Lina and her friends come out of hiding, the clone Rezo attacks Sairaag. Gourry fights back with his Sword of Light and the others use magic incantations. Even though they fight a close battle they don't have the means to defeat him. In the nick of time, Lina appears with the Blessed Blade in her hand. They are encouraged by seeing a recuperated Lina and together our heroes fight with a renewed tenacity. The Blessed Blade absorbs the evil spirit out of the clone Rezo and he dies shortly after.