A common criticism of Boruto is that it introduced the concept of Naruto's Kaguya and the Otsutsuki clan as aliens, which many felt was inconsistent and came too late in the series. However, Naruto: Shippuden actually foreshadowed this twist in episode #460 when it hinted at the extraterrestrial nature of the Otsutsuki through Kaguya's backstory.
In the original manga by Masashi Kishimoto, Kaguya's story only covered her sealing and the creation of the moon. However, the Naruto: Shippuden anime adaptation expanded on this in episode #460 by providing Earth's first record of her. Kaguya appears as a glowing ball in the sky, which transforms into a human upon landing on Earth. Because of this, the Earth's shinobi refer to her as a "celestial maiden." Kaguya later identifies herself as the protector of the God Tree, which is seen earlier in the anime as descending from the heavens on a meteorite.
Naruto Shippuden's God Tree Hinted That Kaguya Was an Alien
Even with prior knowledge of these scenes, it is understandable that some might conclude that Naruto initially depicted Kaguya and the Otsutsuki as gods, rather than aliens. The use of the word "celestial" when referring to Kaguya by the shinobi evokes the image of a deity rather than extraterrestrials. However, a crucial clue to Kaguya's origins lies in the arrival of the God Tree. It comes to Earth on a meteorite, and meteorites are commonly associated with outer space and extraterrestrials. Conversely, gods are typically linked to dimensions beyond normal space. This distinction is important because Kaguya declares herself as the guardian of the God Tree. If she were a god, it would be expected that she would use her divine powers to transport the God Tree to Earth, rather than relying on a meteorite. Gods are believed to possess abilities that transcend the need for physical transportation.
In addition to these evident clues, Kaguya's story in Naruto can be traced back to her namesake from Shinto mythology, who is known as an alien from the moon. This connection bears some resemblance to how Kaguya in Naruto transforms into the moon when she is sealed as the Ten-Tails. Therefore, exploring Kaguya's mythical roots points to an extraterrestrial origin rather than a divine one. However, it should be noted that a thorough understanding of a series should not depend on fans researching specific characters. This is why the foreshadowing in Naruto, regarding the arrival of the God Tree on Earth, is crucial in setting up the twist involving aliens in Boruto. Boruto simply confirms what was already hinted at in Naruto: Shippuden years prior.
Boruto Actually Justifies Kaguya's Alien Origins
Some may not be pleased with Naruto: Shippuden suggesting that Kaguya originated from a different planet. Even though the inclusion of the Otsutsuki clan in Boruto gives more context, the idea may still feel out of place when considering the fantastical elements of Naruto and Shippuden. Nevertheless, it is unfair to criticize Boruto for a poorly executed retcon since Naruto: Shippuden effectively hinted at Kaguya's extraterrestrial identity, as effective foreshadowing aids in making the improbable more convincing.
You can stream Naruto: Shippuden on Crunchyroll.