Boruto had a flashforward that was initially meant to give the audience a tease of the main conflict in the story, but for the longest time, it was reviled because it seemed to give away a lot of information. However, as the chapters of the manga have progressed, writer and artist Mikio Ikemoto has managed to manipulate this flashforward to make things a lot more interesting for the reader, changing its meaning and context as time went on.
It was stated by original franchise author Masashi Kishimoto that the Boruto flashforward was a last-minute addition to the manga, which makes Ikemoto's usage of that scene throughout the story all the more impressive. There are several red herrings in the manga that seem to hint at this moment but deceive the reader, adding more questions to the context of that interaction between the protagonist and Kawaki.
Disclaimer: This article contains spoilers from the manga/anime and reflects the opinions of the writer.
Explaining the storytelling success of the Boruto flashforward

The flashforward in the opening scene of the manga features the titular protagonist and Kawaki about to face each other in the ruins of Konoha, with the latter telling him that he is going to send him where he sent the Seventh Hokage, his father Naruto Uzumaki. From the get-go, this suggests that the two characters are going to get older but also puts the reader in a mindset of paying attention to every little detail.
For example, Kawaki is the most obvious example since he is not a part of the cast at the beginning and is later introduced as someone who is adopted by Naruto, with fans already thinking of a tragedy, claiming that he took the Hokage's life at some point. However, Mikio Ikemoto plays with people's expectations and later reveals that he actually sealed Naruto and Hinata in another dimension, claiming that he is going to do the same to their son in the flashforward.
There is also the fact that the ending of the first half of the manga and the beginning of its second half establishes that Kawaki wants to take the life of the protagonist. But this flashforward has him claiming that he is going to send him to the same place as Naruto, meaning that he is going to seal him instead of killing him or that perhaps he is eventually going to murder the Seventh Hokage.
Other elements

Another element that has built a lot of expectations is Boruto using the Jougan, which already had its moments in the Studio Pierrot anime adaptation. Fans know that this moment is going to happen at some point and are eager to see how it plays out, especially considering that this dojutsu could help him with the inner conflict he is having with Momoshiki.
Furthermore, Ikemoto also establishes Kawaki with an outfit that he is yet to wear in the Two Blue Vortex portion of the story and wielding a staff, which is now weird in context because he fights without weapons of any kind. This, in turn, creates intrigue about what is going to happen with his character in the coming arcs.
Final thoughts
Ikemoto and Kishimoto have set up a situation where Boruto and Kawaki are bound to clash, and as a result, created a lot of questions and theories that have carried the narrative in a good way. In that regard, this is perhaps one of the sequel's best ideas as a whole.
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