The reveal of Kaguya Otsutsuki as the final antagonist of Naruto surprised a lot of fans. Madara Uchiha was the one who was hinted to be the ultimate antagonist of the series, according to some fans.
Madara was one of the founders of the Hidden Leaf Village and after he lost against Hashirama, he passed his will to Obito Uchiha to live by his name. After Madara was reborn during the Fourth Great Ninja War, Obita had already realized that he was wrong in trusting Madara. But it was too late as Madara got what he needed.
After activating the Infinite Tsukuyomi, Madara inflated and Kaguya Otsutsuki emerged from inside him. Kaguya's sudden entry as a strong enemy didn't stand well among most fans, but was her entry referenced earlier in the series? Fans have noticed an uncanny resemblance between Kaguya and Kimimaro which could relate to Kaguya's foreshadowing.
Naruto: Discovering Kaguya Otsutsuki's Foreshadowing in Kimimaro
Kimimaro was a shinobi who belonged to the Hidden Sound Village after he was retrieved by Orochimaru. He was the last survivor of his clan and Orochimaru saved him because he wanted his kekkai genkai, the Corpse Bone Chain.
Corpse Bone Chain gave its users the ability to manipulate every bone of their bodies however they wanted. They could also take bones out of their bodies and use them as an offensive weapon against their enemies.
As Orochimaru was about to take over his kekkai genkai, he fell extremely ill which led to him retaining his powers and becoming a loyal shinobi for the former. Kimimaro also received Orochimaru's cursed seal, which was the successful one just like Sasuke and Anko.
After Sasuke left Orochimaru's side, the Sound Four were sent to retrieve the former but they failed. As they didn't return, Kabuto awakened Kimimaro to go get Sasuke from Hidden Leaf Village. Juzo, another one of Orochimaru's followers, advised him not to go as Kimimaro's health is fragile as compared to a normal shinobi.
But he left anyway, thanking Juzo for being there for him. As he closed in on Sasuke, he fought Naruto Uzumaki once and overpowered him pretty easily. As the latter was about to be taken down by Kimimaro, Rock Lee made an entrance and saved Naruto.
The fight got interesting as Rock Lee was more of a match against Kimimaro's technique. Unfortunately, Rock Lee was also overpowered until Gaara made an entry to save him. And it was during this fight, a revelation was made that could link to the arrival of Kaguya Otsutsuki later in the series.
Kimimaro belonged to the 'Kagura clan.' This clan was the direct descendant of the first Otsutsuki that came to Earth, Kaguya Otsutsuki. As her descendants, some of the members of this clan received a derivative of her Kaguya's Kekkei Moura (the All-Killing Ash Bones).
This derivative was the Corpse Bone Chain that Kimimaro inherited from his clan. This clan was famous for being a barbaric one and was eradicated after they fought to death amongst one another.
Many fans speculate that the reveal of Kimimaro's clan early in the show could be a foreshadowing of the arrival of Kaguya Otsutsuki during the Fourth Great Ninja War.
The fact that Kabuto and Orochimaru ignored the background of such a mysterious character could signify the arrival of a grand villain later in the series. But there hasn't been any official confirmation regarding this.
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