It's also seen entirely from the perspective of children, none of whom fully understand what's going on. There's an acceptable backstory to everything -- yes, even the ending -- but the show itself doesn't explain anything. That's all in secondary materials, little of which was translated.

(Well, it's based on a novel series. Does that count as 'secondary'?)

If you assume a rational universe, you can probably figure out most of it. Or if you're interested, poke me sometime and we can chat about it. It is, admittedly, one of my very favorite stories.