They don't have to know about keyblades and other worlds but yes, they exist at some point. Yes, there were probably heartless.

We decided to go with as little information as possible so players can jump right in the game, but it's obvious it's not helping you. I'll have to beef up these sections in a little bit. Just make up the stuff? I imagine Xigbar is an Aquarius (Joking of course, no idea what he would be. Not an XigBar player.) What other information do you want to know? Ask away, I don't mind.

I'm happy you're excited and you have plenty of characters to choose from.