Warning: contains spoilers for Chapter 70 of Boruto
The Otsutsuki Clan from Boruto and Naruto may no longer be physically present in the world. Still, as Boruto #70 strongly suggests, they have viable means of returning in some form through the Kama seals inscribed on Boruto, Kawaki, and Code. Their return would not only be problematic for Naruto and Konoha Village but also would put a major crimp in Otsutsuki Clan relations.
As Boruto #51 points out, originally, Isshiki and Kaguya Otsutsuki were sent to Earth to cultivate a God Tree and harvest the chakra fruit it produces every 1,000 years. The fruit is the source of the vital energy members of the Otutsuki clan needs to sustain their success. Rather than harvest the chakra fruit, Kaguya ate it, then attacked Isshiki leaving him dead. Subsequently, through Kaguya's manipulations, the God Tree was transformed into Naruto's monstrous Ten-Tails Beast. However, the Ten-Tails Beast can be transformed into another God Tree by sacrificing an Otsutsuki, or an Otsutsuki vessel, to a Ten-Tails Beast.
Boruto #67 reveals that in sacrificing his spirit to allow Boruto to live, Momoshiki Otsutsuki rewrote Boruto's genetic code such that he is biologically more Otsutsuki than Uzumaki. While it seems that his sacrifice means that he can no longer take control of Boruto, it does mean that an Otsutsuki remains on Earth via Boruto. While this fact would not be an issue if no other Otsutsuki were present on Earth, the act remains that the clan has sent four of its members to Earth to harvest the God Tree. Chances are they will send others, and when they find no God Tree existing, they are likely to think that Boruto could make a useful alternate sacrifice than one of their own.
However, an even more likely scenario is that Issihiki will at some point manage to resurrect himself either through Kawaki or Code. Once returned, Isshiki, who has been dedicated to his mission of growing and harvesting a God Tree, will continue on with this quest. Naturally, knowing of Boruto's connection to Momoshiki, rather than sacrificing himself to the Ten-Tails beast, Isshiki will, in traditional Otsutsuki fashion, likely target another Otsutsuki as the sacrifice necessary to appease the Ten-Tailes Beats, to grow a God Tree and ultimately harvest its chakra fruit. Currently, the "other" Otsutsuki present on the Earth is the Otsutsuki-Uzumaki known as Boruto. Alternatively, being that Boruto is, at this point, more Otsutsuki than Uzumaki, there is also the possibility that the true Otsutsuki nature arises in him. As such, he could target Kawaki, Code, or both to sacrifice to the Ten-Tails beast and return another God Tree to Earth. While this may seem a bit far-fetched, the history of the Otsutsuki Clan, and the inter-relations within it suggest that these scenarios are quite possible.
The return of the Otsutsuki Clan, which has been strongly suggested in current issues of Boruto, will naturally be a threat to Naruto and Konoha Village. The more interesting and important result of their return will be the dynamics between the current vessels of the Otsutsuki spirit, namely Boruto, Kawaki, and Code, and whether those dynamics will lead to a resurfacing of the age-old, inter-Otsusuki Clan dangerous liaisons. If so, the Otsutsuki Clan may have more to worry about than any ninja.
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