The first arc of any anime is one of the most important parts of the entire series. It's usually viewers' first real impression of the story and often decides whether or not they want to continue watching. This high level of importance makes them quite tricky to nail as they set the base for stories that may grow to last hundreds of episodes. The Kazekage Rescue Mission arc from Naruto Shippuden is a great example of a sensational first arc.
Shippuden, serving as the sequel to the original Naruto series, had a more difficult task than the usual opening arc. Team 7's rematch against Kakashi was only the tip of the iceberg of greatness that is the Kazekage Rescue Mission arc. As the story's events unfolded, several of Shippuden's most important plot points were brought up and discussed to some extent. Here are a few overarching themes its debut arc introduced.
Cooperation Among the Hidden Villages
The state of the ninja world was described as one of anarchy in the original Naruto. Though they were at peace with each other, each nation was quite wary of the next. They carefully monitored the balance of power and would seize any opportunity that arose to increase their military might or destabilize the other nations.
During the Sand Village's hour of need, Granny Chiyo never expected the Hidden Leaf to send any real help. To her surprise, Tsunade sent two skilled teams that saved Gaara's and Kankuro's lives. That gesture of goodwill, especially after the part the Sand Village played in the third Hokage's death, strengthened the two nations' bonds and sowed the seeds of what would eventually become the Allied Shinobi forces.
Kazekage Gaara's testimony about the alliance of the Sand Village and the Hidden Leaf was instrumental in forming the Alliance, without which the Fourth Great Ninja War would've been lost.
The Jinchuriki and Tailed Beasts
Though it was common knowledge at this point that both Gaara and Naruto had Tailed Beasts within them, the term Jinchuriki had never been used before in reference to the duo. On their rescue mission in Shippuden, Kakashi and Granny Chiyo explained why the Akatsuki was targeting Gaara and revealed the existence of seven other Tailed Beasts that hadn't previously been mentioned.
While it's never said exactly how powerful and diverse these beasts were, later Shippuden arcs did a great job of developing them further. Their importance to the story cannot be overstated. The Fourth Great Shinobi War was fought to determine the fate of the final two remaining Jinchuriki, Naruto and Killer Bee. The reanimated Jinchuriki also served as powerful antagonists toward the end of the story, introducing even more diverse jutsu to the Naruto world.
Naruto's Relationship with Kurama
Naruto never had a stable connection with the Nine-Tailed Fox within him, but he'd always had it under control for the most part. Shippuden's Kazekage Rescue Mission arc illustrated how volatile their relationship had become and teased fans with a glimpse of Kurama's incredible power.
Upon realizing Gaara's "death," Naruto flew into a rage allowing the Fox to momentarily take control over his body. Luckily Kakashi was there to stop him before the Fox got out of control, but that instance showed how Naruto's emotions would be the key to controlling Kurama. Fans also learned that Kurama was capable of taking over Naruto's body completely when the Jinchuriki felt extreme anger, like he did at Tenchi Bridge in the fight against Orochimaru and after Pain stabbed Hinata.
Naruto's infamous group of rogue ninjas were referenced quite a bit in the original series but their proper debut came in Shippuden. Apart from Itachi and Kisame, the main villains of the Kazekage Rescue Mission arc were Deidara and Sasori.
The duo could not have been a better introduction to the level of ninja Naruto and Team 7 would find themselves up against time and again during Shippuden. Along with having great banter, Deidara and Sasori's abilities expanded the scope of what Naruto fans believed possible with chakra. If it wasn't already clear this group was not to be trifled with, Deidara succeeded in defeating Gaara during his first fight.
The rest of the Akatsuki weren't properly introduced during the Kazekage arc, but that only served to drive up viewers' interest in the mysterious group. Entire arcs were dedicated to defeating some members of the Akatsuki, and each proved they were far from pushovers. The casualties they left in their pursuit of the Jinchuriki spurred the development of several side characters and their influence stretched all the way to the end of Naruto Shippuden.
The advanced form of the Uchiha Kekkei Genkai was first mentioned near the end of Naruto's Sasuke Retrieval Arc. At that time, all that was known is that it was a more powerful Sharingan. It was only after Kakashi unveiled his own that its true potential was made apparent.
Along with greater perceptive abilities than a regular Sharingan, the Mangekyo Sharingan gave its user access to entirely unique and individual powers. Itachi's Tsukuyomi made his genjutsu the stuff of legend and Kakashi's Kamui saved the entire Konoha squad from Deidara's final explosion.
The dangers of the Mangekyo Sharingan were also touched on during Kakashi's battle against Itachi. As a taunt, the Copy Ninja asked Itachi how much his eyesight had deteriorated, referencing the side effect of the new Sharingan's overuse. Kakashi was also rendered bedridden by the end of the mission since he overextended his power when chasing Deidara.
Madara Uchiha ended up being the primary antagonist for much of Shippuden in one way or another, so it's appropriate that he was first teased so early. Madara himself didn't show up until the final arc, but one could argue it was his legacy that set all the events of the series into motion. The mere mention of his name by an imposter provided the extra push for the Shinobi villages to work together, and his appearance showed why their cooperation was absolutely necessary. In decimating the Allied Shinobi Forces, Madara proved exactly why his name struck fear in the hearts of everyone.
The introduction of these plot points so early in Naruto Shippuden helped viewers get acquainted with them and made their reappearances later on seem like natural additions to the story. It built anticipation moving forward and prevented Shippuden from having to info-dump so much when they started to get more of the spotlight. The final cherry on top? The Kazekage Rescue Mission arc even works great as a standalone story.