Boruto Uzumaki is the protagonist of Naruto's sequel, Boruto: Naruto Next Generations. The series is set years after the conclusion of the Fourth Great Ninja War where both Naruto Uzumaki and Sasuke Uchiha ended up establishing an era of peace. Naruto was made the 7th Hokage years after the conclusion of the war, while Sasuke Uchiha roamed the world in an attempt to maintain peace all over.
While Naruto and Sasuke were both uncontested in terms of power after the war, things get shaken up in the Boruto era. Specifically, at the beginning of the Boruto series, which starts with a Prologue, it is believed that the age of ninjas is finally over. Naruto Uzumaki is believed to have died while Sasuke Uchiha is nowhere to be seen, and Boruto Uzumaki is carrying his sword and wearing his clothes, implying that something has happened to Sasuke as well.
The Prologue Of Boruto
Boruto: Naruto Next Generations starts on a very interesting note. The series actually gives the fans a glimpse of the future, four years from the actual timeline of the story, and in this future, Boruto Uzumaki and Kawaki are fighting atop the Hokage faces. Their surroundings are completely destroyed, meaning Konoha was attacked. No shinobi can be seen around them and the two end up exclaiming that the age of Shinobi is finally over. Kawaki also goes on to say that he will send Boruto to the same place where he sent the 7th Hokage, which implies that something happened to the Hokage.
While at first, fans assumed that Naruto Uzumaki was dead, the recent events of the story finally explained that he was sealed away in a different dimension by none other than Kawaki himself. It is very interesting to note that Kawaki also claims that the age of Shinobi is over, meaning that no shinobi is around anymore. Boruto then goes on to say that he is a Shinobi and he is still standing, meaning that he is the last shinobi and the hope of their kind. This implies that something has happened to Sasuke Uchiha as well and spells danger for everyone's favorite Uchiha swordsman in Naruto.
Sasuke's Kusanagi Sword
What further solidifies the fact that something might have happened to Sasuke is Boruto's new attire. Fans already know that Boruto Uzumaki carries the headband that once belonged to Sasuke Uchiha. This headband was entrusted to Boruto by Sasuke himself and to Boruto, this brings a lot of courage and reminds him of the hardships that he went through to earn the recognition of both Sasuke and Naruto. But, that is not the only thing that Boruto Uzumaki is wearing that formerly belonged to Sasuke. Boruto is also seen wearing Sasuke's cloak for some reason. While this could simply be a sign of him training under Sasuke over the timeskip and, thus, attaining clothing similar to him, it could also be the fact that he gained this cloak after Sasuke fell in battle.
That certainly isn't all. Boruto Uzumaki is also seen carrying Sasuke's sword. This sword holds great significance to Sasuke Uchiha as it has served him his entire life, although it has undergone quite a few changes. Sasuke calls his sword the Kusanagi Sword. Originally, the Kusanagi sword was wielded by none other than Orochimaru. However, after Sasuke trained with him, he ended up getting his own sword which he also named the Kusanagi Sword. Unlike Orochimaru's sword, Sasuke's did not have any special properties. However, it served him very well in combat. Sasuke used this blade throughout the Naruto series, until the point where he lost it in the fight against Kaguya Otsutsuki. However, after the war, Sasuke ended up replacing it with a new blade that he also calls the Kusanagi Sword. This sword has been with him in battles against the likes of Kinshiki and Momoshiki Otsutsuki, along with other monsters such as Isshiki. After the timeskip of Boruto, however, the sword is seen wielded by none other than his student.
Why Boruto Carries Sasuke's Sword
Judging by the way Boruto's timeskip has taken shape, it looks like Sasuke Uchiha has entrusted his sword to Boruto Uzumaki. This is supported by several facts — the first one being that Boruto wears his cloak. This is a big indication that Sasuke Uchiha has trained him in combat and, at the same time, has entrusted things to him. At the same time, Sasuke giving Boruto his sword is also symbolic in the same way. Where Sasuke can't deal with the threat posed by Kawaki, Boruto Uzumaki will save the ninja world in the process. The fact that Kawaki claims that the age of Shinobi is over effectively means that Sasuke is not around to save the village.
Whether this means that Sasuke is dead or incapacitated remains to be seen, however, given how big a fan favorite he is, it would be wiser for fans to bet on him being incapacitated and alive, rather than dead. Nonetheless, the fact that Boruto carries Sasuke's sword means that Sasuke is not in fighting condition and out of commission for a significant portion of the story in Boruto. Fans should be preparing themselves for Boruto to follow in the footsteps of his mentor and take over after he leaves things to him.