
You will start by following the characters since their first days in the academy, and you will start to watch them grow every episode, you will know their life, their personalities, love some, and hate some, you will understand them and how they feel toward each other, and witness every single piece of event that made them arrive to what they are in the Shipudden part. There are several reasons of why you should watch the first part (or at least read the manga):

Considering that it's very unlikely to see Obito come back to life or Kakashi gain the Sharingan again, the only option left to free Naruto is for Sasuke to recover his Rinnegan.You don't really have to watch the first part of Naruto before the Shippuden part, but I strongly recommend you to watch it. Sasuke, on the other hand, lost his Rinnegan more recently, after a Momoshiki-possessed Boruto stabbed him in the eye.

However, Obito is dead, and Kakashi lost his Sharingan during the Fourth Shinobi World War. Obito and Kakashi's Magekyo Sharingan had the Kamui power, while Sasuke used his unique Rinnegan ability during his battles against Kaguya and Isshiki to pursue them to other dimensions. Some space-time ninjutsu, however, have been able to mirror this effect. The Otsutsuki are experts in space-time techniques, all deriving from their Yomotsu Hirasaka, and they have displayed the ability to freely travel through different dimensions through the series.

Daikokuten was a technique of Isshiki, which Kawaki inherited through his Kama, and allows the user to store objects and people in a dimension where time does not flow. Knowing that Naruto will try to stop him, Kawaki traps him and Hinata in the Daikokuten dimension using his Kama Rift technique, before heading to kill his adoptive brother. After realizing that Momoshiki's spirit is still inside Boruto, Kawaki comes to the conclusion that the only way to protect Naruto is to eradicate all the Otsutsuki, including his son Boruto. The former vessel of Isshiki Otsutsuki is obsessed with protecting his rescuer and adoptive father, Naruto.

Chapter #77 of Boruto has shocked fans by revealing Kawaki's betrayal of Konoha.
