Prince Oscar of Farsas and his assistant Lazar sneak out of the castle and go to an azure tower in the middle of nowhere. Their mission: to meet the Witch of the Azure Moon, who grants a wish to anyone who can reach her at the tower's summit. Oscar then goes through a series of puzzles and challenges as he climbs the tower. Midway through the stairs, it's revealed that the last person ever to successfully reach the top was the prince's great-grandfather, King Regius, around 70 years ago. When the two enter the final room, two demon statues come to life and attack them. Prince Oscar successfully defeats the statues, but the floor beneath them starts to collapse, causing Lazar to fall. The prince enters the room where the witch resides, and he is greeted by the witch, named Tinasha. Tinasha was surprised to hear the prince was related to Regius, and her familiar noted that Lazar was asleep at the bottom of the tower, unharmed. Prince Oscar explains that another powerful witch, the Witch of Silence, placed a curse on him that would kill any woman with whom he tries to have a child and asks Tinasha to lift it. The curse proves to be beyond even Tinasha's ability to break, so she tries to search for a woman strong enough to withstand the curse. Oscar gets Tinasha to admit she could survive the curse, so he changes his wish as the tower's champion from Tinasha breaking the curse to her becoming his wife. Tinasha adamantly refuses, but Oscar persists. Neither side backs down, so Oscar makes a compromise, requesting that Tinasha leave her tower and live with him for one year as his bodyguard. Finding the wish more reasonable, she agrees and returns to Farsas with Oscar and Lazar.

Tinasha moves into the castle, but insists on keeping her identity hidden. As part of her role as protector, she casts a spell on Oscar negating any magical or physical attack on him. While walking in the hallway with Lazar, she finds out that all the prince's cousins went missing, leaving him as the only royal left. While walking in the hallway, she saves Sylvia from a falling chandelier with her magic. After helping Lazar, Tinasha notices General Als and Meredina sword practicing: Tinasha decides to spar with the general and wins. While walking through the castle, one of her familiars, Litola, informs her of a surge of magic power in the magical lake in Druza. She asks permission from Oscar to investigate, but he comes along with a squad of soldiers. Once they arrive at the lake, they find out that a Druza Mage, whose master was beheaded by Tinasha, is trying to release a demonic beast she sealed away 70 years ago. The mage exposes Tinasha as the Witch of the Azure Moon to Oscar's troops before wounding a few of the soldiers and fleeing. Tinasha again asks the prince to let her progress alone: Oscar relents but makes her promise to come back safely. Tinasha fights with the mage and kills him and his followers before they can remove the seal, sparing only one. She then removes the seal herself and fights the beast. Tinasha prevails after a fierce battle, but the beast bites her as she casts her final spell. Her pet dragon carries the wounded witch back to Oscar, who immediately takes her back to Farsas for healing. After some time, the mage noted that Tinasha healed herself, but as a result she aged rapidly and now has the body of an adult.

After petting her familiar, Sylvia caught Tinasha trying to cut her hair, which grew as a result of her rapid aging, with a dagger. After getting over her panic, Sylvia cuts it for her. Oscar introduces Tinasha to his father the king, revealing that she is the Witch of the Azure Moon and declaring his intention to marry her. Two mages, Valt and Miralys, are at the lake where Tinasha slew the demonic beast and take a crystal that the beast dropped after the battle. A mysterious man arrives and tells them that he is trying to find Tinasha and attacks the duo when they try to leave. Valt teleported Miralys to safety leaving him to be vaporized by the man. Oscar and Lazar escape the castle to go to the Byle Forest, where nine villages were found killed by mysterious plants that attacked them. While out in the forest, a plant releases poison that knocks out Lazar, but a mysterious woman arrives and takes him to her cabin for to save him. While there, she introduces herself as Lucrezia, the Witch of the Forbidden Forest and longtime friend of Tinasha. After hearing of Oscar's intention of marrying Tinasha, the witch offers the prince an aphrodisiac to attract her, but he refuses. After returning home, Oscar begins to act strangely, and Tinasha senses something amiss. While she originally thought he simply wasn't getting enough sleep, she figures out that he was cursed by Lucrezia. She then scolded him and told him that she would break her curse when he was asleep. Later that night, Oscar was dreaming of being with Tinasha in bed, only to strangled her to death. Oscar wakes up in a panic, and Tinasha informs him the curse is broken. Oscar, still upset over the dream, tells her he never wants to kill her. Tinasha scolds Lucrezia for cursing her ward, but the older witch apologizes and give her samples of Oscar's body fluids to help with her research into his curse. She also tells her that Oscar cherishes her. Tinasha returns to Oscar's office and apologizes for the trouble Lucrezia caused.

Oscar asks Tinasha to spar with him even allowing her to use her magic on him. Kagar, an envoy from the nation of Cuscull arrives and requests an audience the Witch of Azure Moon, but Oscar lies to him that she is not in the castle. While Tinasha is finding Oscar, she meets Oscar's maid Miralys who got the job through her relative General Ettard, then meets with Lucrezia for tea. After calling Tinasha "Lady Aeti", Oscar finally has Tinasha to meet the envoy. The envoy asks her to come to Cuscull and teach the mages there, but Tinasha refuses to help someone who didn't even bother to climb her tower. After meeting Lucrezia in the castle's hallway, it is discovered out that Cuscull is a nation consisting of mages who proclaimed independence. Suddenly, Meredina attacked the three and harshly insults Tinasha, telling her to leave the country. After hearing that, Tinasha becomes gloomy and Oscar comforts her. Lucrezia discovers that Meredina was under mind control. Later, Tinasha teleports Oscar to the tower and asks him to spar her there for a few days after she sends her familiar to Cuscull. One day, after finishing his training, a group of adventurers arrives at the tower. Tinasha tells them that if they defeat Oscar she'll grant them their wish. After defeating the adventurers, Tinasha declares the training complete. Tinasha's familiar returns from Cuscull and tells them that there are around two hundred mages in the nation, more than any other nation, which could mean they are planning a war. Suddenly, news breaks that General Ettard died, and the entire castle gathers to mourn. Miralys kills Kagar after he kills Valth.

Tinasha dreams of her past, where she is being carried by somewhere by a man, only to wake up and find Oscar carrying her to bed after she fell asleep while sitting. Later, the king summons Oscar: Tinasha found out that Miralys is capable of withstanding Oscar's curse, making her a potential bride. Oscar was oblivious to her magic powers and questions her. She reveals her magic was sealed by her mother and Master Kumu. After noticing Tinasha has been missing for a few days, Oscar climbs the tower again to see Tinasha analyzing his curse with Lucrezia. Back at the castle, General Als tells Tinasha that there is no background history for Miralys. Now suspicious of her, she and Als test the young maid, pretending to hug intimately in plain view to see how she reacts, but Oscar also sees this. He calls Tinasha, puts a magic suppressing wristband on her, and carries her to bed, seemingly to force himself on her as punishment. Recalling her dream from earlier, Tinasha gets angry and her magic flares out of control. Oscar immediately calms her down and apologizes, stating that he was only trying to scare her. Knowing Miralys is suspicious, he tells her father that he will only marry Tinasha no matter what happens and calls for a more thorough investigation into Miralys. The maid then and attacks the two, blinding Tinasha's left eye and summoning a smaller version of the demon beast from Druza. Oscar and Tinasha fight the beast and Miralys respectively, but Tinasha decides to cast a stronger spell, forcing Oscar to fend both assailants off to buy her casting time. He kills the beast and Tinasha casts her spell, but Miralys escapes to the treasury, finding what she was looking for. Tinasha binds her with a spell, but Miralys used magic to make her soul disappear, leaving a living but functionless body behind. Tinasha heals her eye and Oscar again apologizes for taking his scare tactic too far.

While Oscar sleeps, Tinasha breaks the curse cast upon Oscar, casting an equally powerful curse with the reverse effect so they cancel each other out. The king said thanks to Tinasha and invites her to King Kevin's birthday celebration and diplomatic ball. Lazar delivers a message to Oscar informing him about the king of Cuscull, Lanak, burning down villages and towns near the nation of Tayiri's border. Oscar assumes it's revenge for Tayiri's persecution of mages. Later, Tinasha suddenly asks Oscar to take official ownership her pet dragon Nark. He agrees, and after the transfer, Tinasha kisses him. Tinasha and Oscar attended the ball, where Oscar meets Princess Cecelia of Tayiri, who's attending in place of her brother. The two go to a private room, Oscar wanting to discuss the attack and Cecilia wanting to flirt, but Tinasha arrives, leading him to throw the Princess out. Tinasha weakens Oscar's barrier and warns him of what's about to happen. Lanak, ruler of Cuscull, then appears, and Tinasha declares that she's leaving Oscar to be with him. Oscar decides to visit Lucrezia for advice, only for her to already be at the castle. Gathering his most trusted allies, he asks about Tinasha's past. Lucrezia reveals that Tinasha, whose real name is Tinasha As Meyer Ur Aeterna Tuldarr, has been looking for Lanak ever since she became a witch. She is also royalty of Tuldarr, a nation that was destroyed 400 years ago. Tuldarr chose their royalty based on who had the most magical power, and being the strongest in the land, Tinasha was expected to be the next ruler while Lanak, though the king's son, would only be her consort. Though they loved each other like family, envy and her alignment with a rival political faction led Lanak to turn against her. One night, he and his allies conducted a ritual to kill Tinasha and steal her power for themselves, but her overwhelming magic broke through the ritual and ran wild. A mortally wounded Tinasha managed to regain control of her magic, but not before it destroyed the kingdom. Having become an immortal witch as a result, she built the Tower of Azure Moon on the former land of Tuldarr to live out her days in solitude. Lucrezia then points out that Tinasha was protecting Oscar from Lanak when she weakened his barrier and gave him everything he needed to track her down. Cuscull demands the capitulation of the Four Great Nations after Tinasha is reported to have attacked five large cities. The king demands that Oscar to kill Tinasha, but he refuses, still intent on marrying her. His father relents on the condition that he should ascend the throne, officially making him the new king.