If you recognize this music,you're the goat. Also if you haven't watched Naruto or Boruto: Naruto Next Generations then be aware of spoilers,get ready,this gonna be a long one. --------------------------------THEORY------------------------------------ In the manga of Naruto shippuden,chapter 687(during the great ninja war) there was this mysterious entity that was shown and has become a Hot Topic in the Naruto community. Some say that it's Boruto that came back to the past raising the epic foreshadowing of Kishimoto(The creator of Naruto & Boruto).While some argue that it's Sakura and that this theory is a stretch.Many of the people deny this theory because of the scene in the in the Naruto shippuden anime that physically shows Sakura in the same place as the figure in chapter 687. At first it may seem like it's actually Sakura,however the animated version of this scene completely chopped off the mysterious entity. A few banners earlier in the manga,Sakura was just beside Obito. Kakashi and Obito then turn their faces and dash towards Kaguya. This means that if Sakura was shown beside Obito then the shadowy figure must have been on a different side of the area.The fact the the anime left out this entity completely could also mean that the animators (like most of us) were unaware of this vital detail also,the figure was standing on top of the cliff while Sakura was shown sitting. Even when Sakura was shown before Obito's death in the anime,she was sitting but lets say it really was Sakura,she couldn't have been at 2 different places around the area in such a short amount of time. Also,at the end of ep 22 of Naruto Shippuden named(:Chiyo's Secret Skills),there were 3 figures in the shape of the Otsutsuki from Boruto that tried to extract Naruto's tailed beast chakra so I wouldn't be surprised if Kishimoto had been working on the story of Boruto ever sense the early days of Naruto. It explains how he was able to make a Boruto reference almost 16 years prior to the show. Now,as to how and why Boruto decided to go back to this time period is most likely because of Eida. As you know,she has the ability to see what has happened in the past and present but the amount of time she can see back is limited seeing as she is 16 years old and cannot see what has happened before she was born. Which means that Boruto going back to the 4th shinobi war(with the power of the Jougan of course) pretty much makes sense mainly because it's the closest point in the timeline were he can bypass Eida. That's about all there is to this theory,thanks for listening!
The Boruto timeskip is just around the corner in the manga and anime. Kawaki and Eida played a key role in advancing the story to the point where Boruto is now targeted by the entire village of Konoha. Momoshiki's warning came true and now Boruto is on is own with nobody to help him.