The Lyoko gang while hiding the existence of Lyoko from everyone else has secrets from even each other.
Jeremy hides the fact that he is adopted because to him his adoptive parents are simply his parents. To bring it up makes him feel as if he's making them lesser than they truly are.
William hides the real reason he was kicked out of his last school. The girls could deal with the love letters, they couldn't deal with his borderline stalking and his parents pulled him out before he crossed the line and got arrested. Kadic was his last chance and ironically he owes Xana because after being freed William wanted to be the best person he could be and changed.
Aelita hides the fact that there was time when she and Xana actually got along. When she would play with the creatures that Xana commanded and even Xana himself. It isn't until years after Xana is destroyed that she realizes Xana was trying to invoke Stockholm syndrome in order to keep her on Lyoko.
Yumi hides just how truly grateful she is to Hiroki. He always seems to know when to annoy her enough to distract her from her troubling thoughts.
Odd hides the fact that he has in fact told people about Lyoko. He only does it when the Xana attack has gone so haywire that the only solution is too return to the past and to him the reset makes it not count.
Ulrich, out all of them hides the most. He hides just how strained his relationship with his father truly is because sometimes Ulrich honestly hates him. He hides the fact he is rich because he knows people will try to befriend him for access to his money. He hides the fact that he once had girlfriend and her cheating on him is what holds him back from confessing to Yumi or giving Sissi a chance. Most importantly of all he hides just how grateful he is for his friends being there.
Secrets are not just limited to the Lyoko gang and others in Kadic have their own secrets as well.
Principle Delmas hides the fact that he has been out on dates. His students don't need to know his business and he doesn't want Sissi to get attached to any of them until he knows he's met someone he truly connects too.
Nicole Weber hides her crush on Principle Delmas because she doesn't want to make things awkward between them.
Yolande hides how uncomfortable she is about being crushed on by the boys at Kadic. She is a little gleeful when administering shots in order to curb the number down.
Jim hides the real reason he began to teach Ulrich Pencak Silat. As a young boy Jim was rather angry at the world, feeling lost and adrift and it wasn't until he looked into the mirror and saw how cold his eyes wear that he decided to go into the army in order to find direction and change himself. Years later when he's working at Kadic he does all he can to help children who felt as he once did and he devotes the most time to Ulrich because he sees a hint of something that unnerves him in those young eyes. He likes to he think he knows what removed it but he's never sure if it's him, Ulrich's friends, or a combination of the two.
Xavier hides how conflicted he is by his parents staying together. He knows (on accident) that they don't love each other anymore but they love him enough to pretend for his sake. He wants them to be happy because he loves them yet hopes they fall back in love with each other while pretending.
Anais hides the real reason she goes out with Odd. She remembers the Ulrich with cold lonely eyes who seemed to slide around, but never stand with anyone. She remembers the young boy who honestly scared her by a growing darkness lurking in brown orbs. As far as Anais is considered Odd is a hero who was able to forcibly shove that young boy lost in darkness into standing in the light.
Tristan hides how uncomfortable he feels in his body. He looks at himself in the mirror and shivers slightly over how he looks.
Nicholas hides why he hangs out with Herb and Sissi. At one point Nicholas liked to image that they were friends but as time moves forward he grows more and more annoyed with Sissi's attitude and tired with Herb complying with her by the second. By sophomore year Nicholas, honestly hangs out with them because he feels like he has no else to go.
Tamiya hides from her feelings. She ignores the voice in her head telling to be closer to Milly because it's safer to hold Johnny's hands in public.
Emily hides brilliance. If someone like Herb is overlooked because of Jeremy, then how could she be seen is her reasoning but deep down she's afraid of being treated like an outcast.
Thomas hides his sex. Everyone else thinks it was a matter of the boy dormitory being overcrowded when Thomas transferred in and it was an oversight that Thomas was left there when Jeremy doesn't have a roommate. Kadic is just strict when in comes to separating the genders and Thomas's parents do all they can to support their "son." The few students in the know keep quit because their Thomas's friends, no matter what.
Johnny's hides how much of a coward he feels. Despite what Tamiya might think he's not blind and yet can't help but let himself be used.
Naomi hides that she's a serial crusher. It's something that can't be helped but she finds herself crushing on one boy for a week before moving on to the next one and repeating the cycle.
Paul hides what he sees. Paul was always been sensitive to the outwardly but is honestly scared of the day when other people learns he can see ghosts.
Caroline hides her musical talent. As a young girl she was forced to play the piano by her father until it was perfect. As a teenage she no longer finds such activities fun and will never be able to forgive her father for it.
Matthew hides his relationship from his parents. He likes Thomas for Thomas and supports him every step of the way. He's just so very afraid of his parent's reaction, especially his fathers.
Valerie hides her love of musicals. It's a guilty pleasure of hers and she just doesn't want anything to know something so private.
Caroline hides her taste in music. She loves heavy metal and doesn't want to have to deal with her friends objections to it as her mother's is bad enough.
Sandra hides her jealously. She's jealous of Milly for being brave enough to approach Ulrich, being liked by Hiroki, and most of all she's jealous that Milly has Tamiya's friendship.
Hiroki hides his envy. When he sees Ulrich and Odd laughing and having fun, he feels a so very envious because he wants Ulrich to be his brother but fears that Ulrich only has room for one.
Theo hides his fears. He fears what lurks within the shadows; he fears the dark, and most of all he fears the monsters with terrifying skull masks and holes in their chests.
It's rather surprising what secrets those at Kadic hide, isn't it?
Author's Note: To anyone who doesn't know Theo is seeing Hallows (from Bleach), which oddly enough Paul doesn't see.
According to the Code Lyoko wiki Thomas lives in the girl's dormitory, either as a mistake on the creator's part or as a sign that Kadic doesn't segregate the dorms by gender. I decided to play around with that in this one-shot.