Ep 1. Kakashi: Sharingan Warrior

Thanks to Naruto's ingenious plan, Kakashi is freed from the water prison. He defeats Zabuza, leaving him critically injured. But in the blink of an eye, a mysterious tracking ninja shows up and kills Zabuza before Kakashi can. Naruto is shocked that a boy, not much older than he, was able to defeat Zabuza so easily.