At the end of the last volume, Tsunade was conflicted and wasn't sure who she would side with, but that answer is known immediately upon the show's opening. She refuses the snake-like villain's proposal and starts up a fight to rid the world of him once and for all, but Orochimaru's henchman, and Leaf Village traitor, Kabuto stands between her and Orochimaru.
When Jiraiya and Naruto finally get to the scene of the battle, they quickly assess the situation and start protecting the woman. Because Tsunade drugged Jiraiya the night before, he isn't much help in the fight, and when Orochimaru summons the giant snake named Mando, it's everything he can do just to stay alive. Meanwhile, Naruto faces off against Kabuto, and finally pulls off the new attack Jiraiya has been teaching him, the Rasengan.
Inspired by Naruto's mastery of such a powerful jutsu, Tsunade calls for her summon, a giant slug named Katsyuu, and Jiraiya is finally able to summon Gamabunta (again, the drugs in his system hinder his chakra abilities). So here we have the tree Sannin riding atop of their gigantic summons getting ready to fight till the death. Obviously, this particular episode is full of action and great to watch.
Once the fight with Orochimaru is done, Naruto, Jiraiya, Tsunade and Shizune (Tsunade's assistant) start heading back to the Hidden Leaf Village, and besides a small stop at some hot springs, they get there without a hitch. It isn't long before Tsunade officially takes on the role of Hokage, and sends Naruto, Sasuke and Sakura on to another mission, this time to help a neighboring land in an odd power struggle.
In the Land of Tea, the trio of Ninja must protect a runner named Idate as he takes part in a race that will allow a more benevolent family in power (as opposed to the group of criminals currently in charge). Of course, the other team has their own hired help in some ninja from the Village Hidden in the Rain.
Interestingly enough, it seems Idate himself has a bit of history with the leader of the opposing ninja, as well as the Leaf Village itself. Needless to say, the race ends in a big fight between Squad Seven and the Rain Ninja; actually, it ends in a fight between Seven and Aoi, the Rain's leader (since Sakura, Sasuke and Naruto were able to take care of the other three fairly early in the race).
Naruto: Uncut Box Set 8 does a pretty good job of not only wrapping up the existing story arc involving the search for Tsunade, but it also completely encompasses her officially taking the title of Hokage (and all the hoopla that comes with that), healing the various people that were injured when Itachi Uchiha came to town, and Squad Seven's mission in the Land of Tea. Which is all good, because Box Set 9 gets the series running into one of the biggest events of the show.