The Worst Client (volume)

Synopsis
Kakashi advises the three to start focusing on the team's well-being instead of their own, and in doing so they are able to pass the test. As one of the team's first missions, they are assigned to to escort a man named Tazuna to the Land of Waves. Along the way, the group is attacked by Zabuza Momochi, an assassin sent to kill Tazuna. Kakashi, with the help of Naruto, Sasuke, and his own Sharingan, is able to defeat Zabuza. Before he can finish Zabuza off, however, a masked boy named Haku arrives to take him away. In preparation for another of Zabuza's attacks, Kakashi decides to train Naruto, Sasuke, and Sakura.