Unless I've misunderstood you Akari, that isn't always the case, as Mike seems to be pointing out the same thing I've also wondered. That is - what about areas you can both disappear behind, as well as walk in front? For example - Chocobo farm. You can walk behind the house on the left hand-side, but you can also run in front of it (to go through the front door, for example). In this way you can both appear in front of and behind the same sprites making up that part of the background, depending on the Z-distance of your character; where is this information stored?