"The Second Critter" (2匹目, Nihikime) is chapter 10 of the original Naruto manga.
Before the Demon Brothers can kill Naruto, Sasuke steps in and stops them. They turn their attention to Tazuna, and Sakura comes to his defence. Before the brothers can land an attack, Kakashi appears and neutralises them, having only pretended to be killed so he could see who their target was. Obvious that protecting Tazuna is going to be more complicated than the C-rank mission they were assigned, Kakashi considers going home. Naruto, angry with himself for freezing up, demands that they complete the mission no matter how complicated it may become, vowing to never step down from a challenge.