Loyal Defender

You know HOW I know I'm a complete idiot?
I went through this place called the Cavern of Remembrance, which is basically like a series of trials for Sora to go through, and at the end is this place known as the Garden of Assemblage. There's this computer in the middle of the room - you interact with it, and data version doors to fight members of Organization XIII come out. You interact with it again, it says this -

I didn't freaking realize the doorway behind it opened up as a shortcut.

So I went ALL THE WAY through the Cavern's difficult challenges TWICE before I figured that out.