Naruto Episode 10
Kakashi rests and recovers at Tazuna’s home. Once he awakens, he concludes that Zabuza is alive, as there were numerous inconsistencies with the hunter-nin’s actions. The hunter-nin is revealed to be Haku, a boy under Zabuza’s wing. To prepare the group for their next fight, Kakashi continues their training by teaching them how to climb trees without using their hands.
Source: Wikipedia
Naruto Episode 10 – The Forest of Chakra
