One of Kakashi’s best moments in Naruto Shippuden was never manga canon. Following the shocking reveal that Tobi was indeed Obito Uchiha, Kakashi was suddenly at the center of Naruto Shippuden’s story. Obviously, Kakashi had been an important character from the beginning, but after the Obito reveal, not only the events of “Kakashi Gaiden” but Kakashi’s entire past became essential to follow Naruto Shippuden’s final arcs. As such, it was no surprise that Kakashi received a 12-episode filler arc.
Throughout most of Naruto and Naruto Shippuden, one popular complaint was that Kakashi was not given much focus. The mysteriousness around Kakashi added a lot to the character, but still, many wanted to learn more about the man who had studied under the Fourth Hokage and who was arguably the most famous Jounin in the Leaf Village. The first piece of significant Kakashi backstory came with "Kakashi Gaiden", a flashback arc released in the manga right after Naruto left the Leaf Village and that was later adapted into a two-part Naruto Shippuden episode. That said, Kakashi’s best flashback arc was not "Kakashi Gaiden".
“Kakashi's Anbu Arc: The Shinobi That Lives in the Darkness”, a 12-episode Naruto Shippuden filler arc, revisits Kakashi’s life right after the death of Rin and the end of the Third Great Ninja War. The “Kakashi Anbu” arc comes right as the Naruto Shippuden anime revealed that Tobi was Obito, a perfect moment to show how the events of the Third Great Ninja War changed Kakashi forever. The arc works as a perfect complement to “Kakashi Gaiden”, and it elevates the Obito Uchiha reveal. There is a level of seriousness and stakes that most of Naruto’s fillers do not feature, which is why many people assume that the Kakashi Anbu arc is canon. Unfortunately, it is not.
The Kakashi Anbu Arc Is Way Too Good To Be Filler
While some Naruto and Naruto Shippuden fillers can be entertaining or informative, none of them are as interesting as the “Kakashi Anbu” arc. By revisiting Kakashi’s life during such a tragic moment, Naruto Shippuden did something that even the Naruto manga couldn’t – It established how a traumatized and aggressive Kakashi became the uplifting, kind-hearted sensei audiences meet in Naruto. The arc goes through all stages of Kakashi’s grief, and it masterfully links Kakashi’s trauma with other important events of the Naruto timeline. For example, Kakashi was still mourning the losses of Obito and Rin by the time the Nine-Tails attacked the Leaf Village.
In fact, the way Kakashi’s story connects with other key events of that time period is what makes “Kakashi's Anbu Arc: The Shinobi That Lives in the Darkness” truly special. Audiences get a chance to see how Danzo reacted to the Nine-Tails attack, how Sarutobi’s decision of becoming Hokage again was made, and how Kakashi almost became loyal to Danzo. Kakashi’s story also connects with that of Yamato and Itachi Uchiha, thus making the “Kakashi Anbu” arc much more than just a Kakashi flashback.
Essentially, “Kakashi's Anbu Arc: The Shinobi That Lives in the Darkness” improves not only Kakashi’s story but Naruto Shippuden’s word-building as a whole. At the end of those episodes, audiences feel like they know much more about Kakashi, which then elevates moments like the Kakashi vs. Obito fight. For that reason, it is disappointing that Kakashi’s Anbu flashbacks are not actually Naruto manga canon.