SPOILER Alert for those who do not want to be spoiled for Naruto/Xenogears
I know this sounds crazy and you're free to disagree with me, but Naruto seems to have a lot of elements in common with Xenogears after Chapter 681.
If you don't know much about Xenogears well you can look it up or play the game, but I will break it down so even those who are not familiar will understand.
How does Naruto parallel with Xenogears?
Naruto + Sasuke = Fei and Elly -
Soul Transmigrants who are crucial to the Resurrection of a God(Kaguya/Deus). Fei was the Contact and Elly was the Anti-type that would complement each other. Same goes for Naruto and Sasuke with Yin/Yang. These soul transmigrants would become crucial to stopping the Gods of their respective universe.
Zetsu = Miang - They are both ageless entities that were created by their Gods for the sole purpose of resurrection by manipulating the entire human race and prepare them as sacrifices. They are the pretty much the cause of all the terrible events throughout the story. Both are entities that were created from nothing and have the ability to possess.
Zetsu, Madara, Obito, Pein = Emperor Cain, the Ministry, Miang, Krelian. - They are instruments for the resurrection but each had a different motive and different desire. Each worked together but at the same time manipulated each other to obtain their own goals and eventually betrayed each other.
Kaguya stole power from the Shinju to become a God = Deus stealing power from the Wave Existence to become a God. The Shinju and Wave Existence are pretty much the true Gods of their universes. This is similar to the concept of Gnosticism with the false deity demiurge. http://en.wikipedia.org/wiki/Gnosticism
Kaguya/Deus were intentionally means to peace. -
Kaguya became a God to stop human fighting, but became consumed by lust for power and became destructive and evil and had to be sealed away. Deus was an interplanetary weapon system created to stop a galactic civil war from breaking out, but it became ambitious and destructive and had to be stopped.
Both Kaguya/Deus had prepared a contingency planned for their resurrection which after many years leads to the stories that we know.
Kaguya/Deus are the alpha and the omega of their universe = they lead to the creation of the humans(ninjas) but will also be the end of humanity.
Fate of Humans - Ninja are consumed with their chakra taken away and turn into weapons in the form of White Zetsus. Humans in Xenogears are consumed by Deus as parts to complete its resurrection and are turned into bio-organic weapons known as Angels/Seraphs.
Kaguya/Deus future plan. - Deus had plan to go into space to cause destruction throughout the universe. Kaguya probably has something similar with her chakra powers and her army of white Zetsus.
This is speculative but I am very certain that Kaguya came from space, she clearly is not human of Naruto's world. Deus came from a different world from the where the story takes place.
This really just something that popped into my head after chapter 681 and recently playing Xenogears after a long time.