No matter how many times I play KH1, I always forget that you don’t actually go through that door. Also sorry I’m still allergic to refs. But even in screenshots I’m convinced Sora could shimmy through there if he wanted. And Kairi would have an even easier time since she’s not burdened with popper pants.
PS if you’re wondering about the Keyblade, it’s stuck through her belt. If you’re further wondering why the hell that works, ask the guy who draws the manga and decided that Sora can do it.