Whoa there, Kingdom Hearts has a serious tone too. Just get past the Disney stages and we got serious business with original plot. And magic is a problem? I think half the Smash characters revolve around magic in one way or another. Look at Zelda, or even Geno for the supporters. Don't throw in magic as an excuse because it's not a solid argument against why Sora would fit in Brawl or not.
I do think that was a bad argument but there are many argument of why Sora should not be in brawl and not many to say why he would be in and still then they are not very good(I know you said fit but I just what to post some arguments to say why he should not).
1. If Sora is in brawl people are going to stat to wanting Donald Duck, Goofy, Merlin, Aladdin and soon after that the characters polls are going to be full of characters like that and it will be hard pick what characters should be in.
2. The Sora is not deserving as they Kingdom Hearts games has only had one game for a Nintendo systems(one more coming out but it does not help a lot and you don’t play as Sora in it) and is mainly on Sony systems.
3. Square Enix’s Final Fantasy series and Dragon Quest series are a lot more deserving, shows what type of games they make better and they have a lot more fans so would help brawl to sell a lot better then if Sora was in.
4. Sora is owned by two companys so it would be a lot hard and would be longer, so it would be at the costs of two characters.
5. One of the bests reasons of why Sora should be in is that he has a Keyblade so would not be a another sword user but a blade is a sword so it is a Keysword.
So here are 5 reasons and there are many more as well.