Since the start of the Two Blue Vortex manga, fans of the series have been counting down to the previewed fight between Boruto and Kawaki. The reason most fans have been waiting for this fight is because they have built up some expectations from it due to the Naruto vs. Sasuke fight in the Naruto manga.
Unfortunately, as it stands, the outcome of the sequel manga fight could be very different from that of the original manga's fight. This is because, unlike the final fight in Naruto manga, in which Naruto defeated Sasuke and brought him back to the village, the fight between Boruto and Kawaki could see the protagonist kill his adoptive brother. This was hinted at by developments in the manga's most recent chapter.
Disclaimer: This article contains spoilers from the Boruto: Two Blue Vortex manga.
Boruto: Two Blue Vortex chapter 13 hints at Kawaki's death

Boruto: Two Blue Vortex chapter 13 finally unveiled Boruto's flashback scene with Kashin Koji. With that, the manga series finally revealed why the protagonist was aware of so many things. Many fans were previously suspicious of the protagonist either having foreseen the future through Momoshiki or having time traveled through the past and present, but that wasn't the case.
Instead, Kashin Koji's newly manifested Prescience Shinjutsu allowed the protagonist to learn about the future. As revealed by Kashin Koji, his ability allowed him to look into all possible future outcomes. These outcomes ended poorly for the world as they saw Kawaki being fed to the Ten-Tails, inevitably leading to the creation of the chakra fruit and the end of the world.

Thus, Kashin Koji proposed a team-up with Boruto to help put a stop to this outcome. As part of this, he even promises the protagonist that he will help him learn all the Jutsu that he will eventually learn in the future, speeding up all his power-ups. The protagonist's only condition was that no matter the outcome, he refused to partake in it if the plan included killing Kawaki.
Kashin Koji did not say anything against this condition. The majority of fans could theorize that the reason Koji did not react was that he was planning to go after Kawaki himself. However, there could be something else at play.

There is a chance that Kashin Koji did not have anything to say about Kawaki because he could not foresee any future where Kawaki would survive. As he revealed, all outcomes Koji had envisioned saw Kawaki being fed to the Ten-Tails. Hence, the only way to bypass such an outcome in the current timeline would be to defeat the Divine Trees. But what if Kashin Koji never survived to envision the future after that?
While Koji's Prescience ability is a Shinjutsu, it is very possible that it has a weakness. As evident from the manga, while Eida can look into the past, she cannot look back at any event that took place before her birth. Similarly, there is a chance that Kashin Koji may not be able to look past any scenario in which he passed away.

Therefore, there is a chance that the only outcome where Kawaki wasn't fed to the Ten-Tails was when Kashin Koji himself passed away. This is why Kashin Koji did not know if Boruto would succeed in his mission to talk Kawaki into restoring the Uzumaki household.
As for Kashin Koji's possible death, there's a huge chance that Kawaki would be responsible for it. As seen in the recent manga chapters, Kawaki was very curious about Boruto's information source. Even later, when he discovers Koji's involvement with the protagonist, he destroys the scientific ninja tool. This development suggests that Kawaki could likely kill Kashin Koji to prevent the protagonist from learning about future outcomes.

Therefore, the previewed fight between Kawaki and Boruto at Hokage Rock could happen after Kashin Koji's death. In this fight, Boruto could be forced to kill Kawaki to protect the world from the worst possible outcome, where an Otsutsuki could feed Kawaki to the Ten-Tails.
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