Leon was a unicorn who took interest in humans and their interactions with each other. Apparently many years ago (it's not specified how many, but it could have been even a century ago) he met a human boy and he got interested in humans. He stole a Fairy Flower from the fairies' garden, seeing as it is known to be able to grant a wish. He uses it to ‘turn human’ expecting the flower to grant him the ability to feel all kind of emotions as humans do, however, the flower only granted him a human form. Leon tossed the flower away after it did not grant his wish to the extent he wanted to, leaving it on Gedonelune Academy ground.
In Leon's main route, Liz Hart finds Leon confused in the forest and brings him to the academy worried for his safety. Leon route mainly revolves around finding the thief of the Fairy Flower, a mystery left open by the previous routes of Joel and Vincent, and the mystery around who Leon used to be before losing his memories.
Leon suddenly appears in the school grounds with no memory of who he is or why he's there. At first, Liz doesn't know what to do and she notices that Leons is holding a beautiful sparkling flower and when Leon tosses it, she reprimends him. Leon doesn't understand why Liz is so upset and she can't explain herself properly. However Leon senses Liz as a pure maiden and kisses her hand in a gesture that he aknowledges this and then dissappears. Liz decides to keep the beautiful flower and encases it in a glass bookmark.
The next day, Liz reunites accidentally with Leon and he is brought back to the academy by her where he is allowed to stay at the school by Headmaster Randolph's orders, even though Professor Schyuler was not convinced in doing so. The headmaster gives Leon an old uniform (which is why he looks different from the rest of the students) and an emblem. When Leon touches it the connection between his and Liz's emblem happen and they become buddies. Which makes Liz responsible for him.
Because of his uncaring personality, Leon at first doesn't think he has to go to school just because the Headmaster said so. Liz finds him wandering early the next morning (apparently he was heading to the forest or possibly the Spring of Unicorns) and convinces him to go to classes with her taking his hand to make sure he doesn't wander off. At first people get a little interested in this new student, but when Leon shows no interest in anyone or anything, they leave him alone. After their second day of class Liz and Leon find a little magical creature who also happens to have no memory of who she is. Liz names her Eress so she can have a name to call her for. Eress flies away hoping she would eventually regain her memories..
During the next ten days Liz takes care of Leon and shows him how things tend to work in the Academy and society. She always goes to the boy's dorms to pick him up and they always walk together to classes and back to the dorms. Also in some occassions she shares her food with him so he can experience new things. In one of the visits to the forest Liz tries to explain to Leon why they should stick together, when Leon understands it a light sprangs from Liz and passes to Leon. After the light sinks in Leon's chest he finds out that what Liz was feeling was kindness and he is able to understand it as well. From then on, when Liz was having a strong emotion she would pass it on Leon in a ball of light. However she had no idea how this was done.
In classes Leon shows unnatural talent for magic as he doesn't use any incantation to do it and being able to cast multiple spells at once, which surprises the professors, including Vincent Knight who was there as both visiting student and professor. There's a special class where Vincent makes a practice of element magic and tells the students to defeat as many Umbras as they can. Each Umbra was made of an element (water, air, fire and earth) and they had to defeat them with their opposite element. The whole class started to fight them, but Leon didn't move not knowing or understanding the point of the exercise. When Liz explained it to him, he used his wand and defeated all the Umbras at once and with a single spell.
After talking to Professor Merkulova and realising he's a gifted wizard, Vincent suspects he's no ordinary human let alone student or a wizard. He even tries to talk to Liz about this but Liz doesn't budge because she's starting to care deeply for him, but she makes sure to tell Vincent that she doesn't think Leon is a bad guy. Later, she admits to herself that she doesn't know much about Leon, so she confronts him about not knowing anything about him. Leon doesn't understand Liz's feelings which causes her distress and makes her enraged with him.
Meanwhile, the weather is starting to change, which is rare since the school controls it and even the students notice these changes. Vincent approaches Liz again and explains to her that the weather is only a part of what was happening and his main corncern was that the forest was withering which also could affect the balance of nature in Gedonelune. He aslo insinuates that Leon might have something to do with it since these changes started when he showed up. She gets furious with Vincent for suggesting that Leon might be behind these terrible things, Vincent confronts her as well telling her she doesn't trust Leon either, but she just wants to hide this fact, otherwise she wouldn't be so anxious.
They discover that the change of the weather and the forest withering is due to Dark Magic. Due to the growth of this dark magic and creatures lurking the campus, many students leave the academy until everything is back to normal. Vincent reveals to Liz that he's actually a Knight, a special elite unit member that was sent to the Academy to investigate about the dark magic that was growing in Gedonelune. She gives her a special badge that would allow her to communicate directly with him in case she finds something odd. Vincent gave it to Liz with the purpose that it would give him some background or information of Leon, but Liz doesn't use until it's practically too late.
Eress returns to Liz and realizes she's a little weak due to the dark magic and the change of the forest. Liz makes her spend the night in her dormitory and puts her in the same drawer where she kept her unicorn book and bookmark. But the next day Eress dissapears and Liz goes find her and, not knowing why, takes the flower with her. Leon joins the search and they go through all the Academy. After a while, Liz drops her bookmark and Leon discovers the flower. He yells at Liz for taking the flower to him. And leaves her screaming that it wasn't his fault. Liz doesn't understand his behaviour and she goes after him but loses his sight.
Vincent and the Headmaster join Liz to find Leon. When they go to the Spring of Unicorns they find a beautiful unicorn with red eyes looking at them. Although the Headmaster and Vincent hesitate to approach, Liz gets closer and hugs the unicorn. The creature transforms in her embrace revealing to be Leon. He apologizes to Liz, Vincent and the Headmaster saying that it was all his fault: Wishing so desperatly to become a human, he plucked a flower from the King of Fairies' garden and asked his wish to come true. However, although he transformed on the outside, remained a unicorn inside, which to Leon made him something close to a monster and since that wasn't his true wish, he tossed the flower when he encountered Liz. He told Liz that after spending time with her and learning of human interactions and feelings, he realized the horrible damage he had done and, not wanting to deal with it, he ran away. Liz slaps him after hearing this last retort. She then yells at him saying that he didn't learn anything then, because the right thing to do for a human was to confront the problem he had caused. Headmaster Randolph then realizes that it's the King of Fairies who was causing the Dark Magic to grow stronger. He explains, that the King of Fairies is the one who controls magic in the forest and the nature that surrounds Gedonelune. Therefore, if he's in distress then the enviroment will suffer as well. Vincent and the Headmaster say they will sort things out now they know what happened and who's behind the Dark Magic. Liz, however, asks the headmaster to let her and Leon resolve things with the King of Fairies. Leon asks this as well since it was his fault in the first place. The headmaster lets them go, although Vincent opposes to the idea of letting Liz go since it was pretty dangerous. But Randolph is confident that Leon can protect her.
Leon and Liz go to the castle of the King of Fairies who has fallen into despair after losing the flower that belonged to his daughter Brunhild, which he interpreted as her death. Leon and Liz appear before him. Also Eress, who now remembered who she was, showed up and ran to aid her father and to tell him that she's still alive. Eress transforms into her true form and along with a powerful light magic casted by Leon they get rid off of the Dark Magic in the King. The King is relieved to see his daughter safe and sound and Leon apologizes properly to the King. Leon tells him he will accept any punishment for he deserved it. The King sees that Leon has changed inside, which is kind of like a miracle for a unicorn, then he announces that he will give Leon time to think over which choise he wants: Either to remain a human but forget the things he had lived and experienced since the day he took the flower or to trasform him back into a unicorn and not lose any of his memories. Leon saw there was a trick and kind of punishment in this: Staying human meant he would make his longed wish to come true, but he would not remember Liz; on the other side, regain his unicorn body would mean that he'd remember Liz and his love for her as well as everything he learned from her, but would have to endure the pain of not being with her. The King gives him a day to think about it, and Liz is left wondering what Leon's answer will be.
Happy Ending- The MC meets Leon outside the girl's dorm and walk to the auditorium together. They walk in silence, the MC feeling sad that this may be their last time doing this together. Leon finally speaks up, asking how MC is feeling. He also mentions that human feeling are complicated, but he understands them now.
Leon makes to wait outside, but Randolph and Schuyler stop him, telling him to stay. The scale of judgement determines that MC is suitable for the academy. The other three in the room congratulate her, and MC decides to hug Leon, getting interrupted by Schuyler. Soon afterwards, it is announced that Leon would also be judged then to determine his suitablility for Geondolune. He accepts the offer, and also passes the trial. Schuyler asks the headmaster if he has lost his mind, to which Randolph laughs, saying that it all worked out in the end. Leon is also told to try and control his power during his stay at the academy. MC is asked again, what magic means to her. Whatever she chooses doesn't matter at this point.
Leon decides to go speak to the King of Fairies about his final decision, and MC follows him. Leon decides that his final decision is to stay a unicorn, in order to remember MC and the emotions that she taught him. The King asks him if his memories are more important to him than his dream, to which he says yes, because he loves MC. Hearing this, the King gives Leon a third option: to be a half-unicorn, human by day, unicorn by night. This would enable him to keep his memories up until now, however, he would never become a full-fledged human. MC asks if he is really okay with that, to which he says what he wants more than anything is to be with her. Telling the King his decision, the agreement is completed, and Leon becomes a half-unicorn.
Outside, Eress apologizes for the magic cast on Leon. She explains that her father's magic is not able to turn one human without taking something in return. MC askes again if he is really okay with this choice, and he tells her that he had no regrets. Eress stops the two, saying that she could add something with her own magic. Turns out the magic would keep Leon human during the night for a few more hours if he recieved a kiss from a loved one. MC realizes the implication that Eress makes, and groans. Eress leaves, and the remaning two are alone in the garden. Leon admits to MC that his feeling for her have grown even stronger, that he followed the path that would lead him to his love.
Leon also wonders how long he will live now, as unicorns usually live for centuries. He's afraid of what will happen if he ends up living much longer than MC, that his world would be filled with emptiness and fright. But MC tells him that they're together for the moment, and that makes her happy. She tells him to live in the moment, and that she will stay with him as long as she lives. Leon tells her that his heart is his greatest treasure, and the memories he makes will build upon it, even if they are painful ones. MC is the light of his life, and he will never lose that light. The couple share a kiss. They look forward to their happily-ever-after ending.
The final episode takes place many years later. A boy and a girl are reading the unicorn picture book by the northern forest lake. The boh asks the girl where she got the picture book from, and she says that it belonged to her great-great-great grandmother. The book is special to her mother. The girl asks if he wants to read the book again, and the boy says sure. However, before they can do so, a stranger asks to join them. The girl asks who he is, mentioning his silver hair. The stranger is revealed to be Leon, alone once again. He tells the two his story of finding his love, once upon a time. He is saddened that she is gone, but the love that they shared together during those years overflows his heart. His memories of her are eternally in his heart. He talks of himself as 'the unicorn', and that he was not alone once he found love.
Normal Ending.- Liz is not accepted as an official student and although she feels down by this news, she decides to follow her own path in her own way. When asked Leon about his decision, he tells her that he has decided to become a unicorn again because he feels he'd rather remember Liz even if it meant not being able to be with her than to remain as human and not only forget her but also forget everything she has taught him. When the King of Fairies sees the unselfishness in Leon's decision and believing he was truly sorry for what he had done with the Fairy Flower (something rare in a unicorn, since they don't have emotions or anything related to them) he grants him to stay human during daytime, but as soon as the sun sets he will transform back into his unicorn form and thus allowing him to have both his dream and his memories.
In this ending Eress doesn't give them the extra hours that she gives in the happy ending. So Liz and Leon decide to live in a village where nobody knows about them and settle there. It's implied in this ending that they remain in touch with their friends from the Academy, since one night Leon approaches Liz from behind and teases her seductively. Liz asks him where did he learn those things, Leon responds that is something that Luca taught him and encouraged to use it with Liz, even though Leon could never understand how Luca could do it with more than one girl, since Leon only has eyes for Liz. Feeling weak due to Leon's caresses Liz is "saved" when Leon loosens his embrace and sensing his "time's up", he transforms into a unicorn. Leon is feeling a little bit frustrated that he can't be with her as human much longer, but Liz then hugs him and tells him how happy she is that they're at least together.
Bad Ending - MC does not make it into the academy. However Randolph tells her not to be discouraged and that she may take the entrance trials when the opportunity arises once again. As she is about to leave the auditorium, Leon bursts in and asks how the judgement went. He expresses his sorrow for her failure to enter the academy, saying that he can see that she does not regret her time at the academy. Leon then steps away from MC and asks Randolph to take him to the King of Fairies. Although MC wants to, Leon tells her not to follow him this time saying he wants to do this alone. He gives her a somewhat sad smile as she leaves the room. It is implied that they never see each other after that point.
Several days later, MC leaves the academy and hangs around the village while waiting for her train to arrive. Just as she is about to leave for the station she sees Leon standing in front of her. However, when MC calls him by name, he asks her how she knew such information, then asks if they met before. As reality sinks into MC, she tells him that they never met, and that he only reminds her of a friend. MC notes how he is able to naturally smile like a normal human being, congratulating him in her mind hat he made his dream come true. He tells her that he plans to travel the world, to which MC says she hopes he enjoys it. MC tells him that she is returning home, Leon tells her he's planning to visit her village at some point. As she leaves, Leon asks MC for her name. She tells him and departs.
Leon notices that tears are running down his face after MC leaves. He repeats her name over and over, more and more tears coming down every time. He sees a smiling face in his mind, but can't remember who it belongs to.
Leon starts out emotionless and uncaring as he lacks the ability to express normal human emotions, however as the story goes on its learn a little bit more about him. He's calm and quiet generally, assuming he is still learning the world around him and social interactions. He’s blunt at times and clearly clueless when it comes to social interaction, but it is shown that he can be quite a caring individual with his interactions with Liz.
Leon posses strong light magic, strengthened magical ability in general and the ability to produce and cast spells without incantations or spoken spells.
- When Leon gains/learns a new emotion in his route, a different coloured ball of light would appear-different colours for each emotion he gained.
- His uniform is said to be one of the school's older designs.
- It's mentioned that unicorns have lapis lazuli colored eyes. However, Leon's are between pink and red.
- Because he's not human and had no family, Leon is the only romanceable character that doesn't have a family name or surname. It's possible that either in the Happy or Normal ending he took the MC's.
- Leon's probably the oldest student in all the Academy since he was a unicorn and they have long lasting lives.
- It's mentioned in Azusa's route that unicorns despise humans and they're quite moody and only liking the company of fair maidens. However Leon's special in that way too, because he was so interested in humans that he wanted to become one. He recognized Liz as a pure maiden, which probably made him more attracted to her.
- It is implied that the little girl in the final episode of the happy ending is in fact Leon and MC's descendant. Although the girl has no idea that Leon is her ancestor.
- In Cerim's and his own route he's appointed in the Fortitudo class. But in Alfonse's route the MC character mentions he was appointed in the Vir Ingeniosus class due to he was misteriously found in the Northern Forest and they discovered he was a genius.
- He appears often in The King of Fairies arc (season 3) but is not until his route that's learned who he is and his role. It doesn't appear neither in season 1 or 2, and he has been shown only in Cerim's route as a new student found out wandering around the Academy. He is only mentioned in Vincent's Sequel when Vincent says that Tsukasa reminds him of Leon. He appears again in Alfonse's route to warn Liz that she was being followed and revealed the person.
- In other routes Liz is shown to be friendly to him and even saved by him, but she even declares that she finds him hard to deal with. The few exceptions are his route when he spends so much time with Liz, that although she struggles with his odd behaviour she also feels so attracted to him and yearns to help him that she never leaves him alone; and the other exception is in the Group Event Story "Swapped!" where there's a stone that swaps minds and Leon ends up in Professor Schyuler's body but he doesn't realize it and even hugs Liz and while nuzzling up against Liz he even says: "I love you, Liz... I'm sleeping with you tonight...", meaning that he and Liz were really closed.
- His wand is silver with a unicorn head at the hilt.
- In his main route, Leon never used incantations when casting spells. However in Alfonse's route he had to recite the intended spell in order to use it.