Oh, boy. [ For a question like this, normally Lea would dramatically plop his butt down on the ground to answer, both for emphasis and because sitting is better than standing about 90% of the time. But since the ground is covered in snow, that's out. So he folds his arms instead and shakes his head. ]

Right, so. The Heartless. They're creatures of darkness, basically. They come in all shapes and sizes, but they all want the same thing: [ he unfolds his arms to casually point to a spot on Tenten's chest ] Your heart.

Under normal circumstances, you'd get like, I-dunno, a handful of natural-born Heartless in any world at a time? They're born out of the darkness in people's hearts, so they'll never actually be eradicated, or whatever. Under normal circumstances.

[ For a moment, he debates over whether to elaborate on why circumstances aren't normal anymore, but that seems like a really long and slightly self-incriminating story. ]

Basically right now, the worlds are kind of in crisis, and there are loooooads more Heartless than there should be. Which is why I said the "worlds went under," earlier. The worst was a year ago.

[ Well, that's not quite right. Yeah, getting to the point of nearly all the worlds being covered by darkness or destroyed or banished to the Realm of Sleep was bad.

But now Lea knows the worst is still to come. ]