Board Thread:Naruto Discussions/@comment-3568954-20140610105302/@comment-1512913-20140610153734

Not really. An alien is technically any organism not natively found in an ecosystem, even bacteria from outer space. If we ever manage to populate another planet, then descendants born to those living on the other planet would in fact be aliens to people on Earth, technically. And after many generations even literary, their bodies would adapt to the different environment.

It all depends on what Kishi plans with Kaguya. There's 3 options:
 * she is a human mutant
 * she is an alien, but most likely a descendant of common ancestor with humans, explaining her on the most part human-like appearance
 * she is not just an alien but also a deity (in comparison to humans anyway) being from a world where her race's members have powers and stuff