As this was an entry for a Writing Contest, you were obligated to use the characters presented/given in the specifics. In this story, it's SHINee. As this is actually more a fantasy story than a realistic one, you still did a great job on making/portraying them as realistic as possible. On top of that, it's a one-shot, which gives you another challenge, so you have to think carefullly on how you will oncorporate your characteristics for each and avery person. Which I can imagine, can't be easy. You can't go too much into detail, because otherwise it will get very complicated and your readers might get lost there. Luckily, you made it work and didn't happen. By the way you let them interact with eachother and the little info we get as background info, we already get a vague imagine on how they are behaving and what their characters can be like. They all have their flaws and "secrets" they keep hidden from one another.

JONGHYUN
He's the main character in your story. He strikes me as a good hardworking person. Someone who goes through fire for his friends. It's like he gives us the feeling he wants to stay partly invisible, because of who is/can become. But otherwise, he doesn't want to be left behind and alone. Luckily for him, he does have friends on whom he can cound and turst when something bad is bound to happen. His best friend, Jinki/Onew, is there to helmphim when he's facing a rough time due to not geeting a certain thing on time (I'm sorry to be so vague, I don't want to spoil anything) Therefor he's very grateful.

JINKI aka ONEW
He's like the eomma of the group. He makes sure everyone is settled and doing their best at school. He also tries to prevent them from going on to the wrong path in their private lives. He's the most caring one of the group. It's like he feels he needs to be the responsable one to watch over everyone. He praises himself lucky with all his friends. He also has a little brother Taemin, whim he is very protective about.

MINHO & KIBUM (KEY)
Those two are more side characters. But they do have their significant role in the story. Without them, it would be so much harder to control the situation. They are the extra support Jinki needs with Jonghyun. To think that those were first enemies due to being in 2 differents departments/houses of Hogwarts. It's quite funny though. They change rather quickly in the story as they do become friends and do care about Jonghyun as well.

TAEMIN
He's the little brother of Jinki/Onew. He's presented to us as this sweetheart of a boy. We don't know that much about him. So it's a bit more difficult to give a satisfactory description about him. We were informed that the story is about the JongTae pairing. In that POV, we can already say that he's the crush of Jonghyun I don't want to psoil anything, but I will only let you know that due to him som "major" changes are taking place.

In general, we can say that almost everyone stays in character and do not undergo major changes. The only 2 people that undergo changes are in fact Jonghyun and Taemin.