"Battle on the Bridge! Zabuza Returns!" (橋上決戦！ザブザ再び!!, Kyōjō Kessen! Zabuza Futatabi!!) is episode 12 of the original Naruto anime.
Haku is picking medicinal herbs in the forest when he encounters a sleeping Naruto, who is exhausted from training. He wakes Naruto, who loudly proclaims that he is training to become stronger (believing Haku to be a girl, and subsequently trying to impress "her"). Haku tells Naruto that only when a person has someone precious to protect does that person become truly strong. Naruto considers this statement and enthusiastically agrees. At Tazuna's house, Sakura and Tsunami are concerned about Naruto spending the previous night in the dark by himself, but Kakashi tells them not to worry. Sasuke abruptly leaves, saying he's going for a morning walk. Back in the forest, Haku leaves (after revealing his true gender to a shocked Naruto), and Sasuke shows up to check on Naruto and scolds him for missing breakfast. The two boys continue their Tree Climbing Practice into the evening, until they finally make it to the top of their respective trees.
Naruto and Sasuke return triumphantly to Tazuna's home, with Naruto cheerful, yet completely drained from the effort. Inari is disturbed at the sight of Naruto, who has exhausted himself for what Inari thinks is a futile struggle against Gatō and his men. He thinks of Kaiza and tearfully tells Naruto that he only thinks he can win because he has not suffered as Inari has. Naruto tells Inari that he is a coward and leaves the table. Later that night, Kakashi tells a despondent Inari that Naruto didn't mean to hurt him. Kakashi continues to explain that Naruto is an orphan who has suffered more than Inari knows and understands Inari's pain better than anyone.
The next day, Team 7 escort Tazuna to the bridge, but leave Naruto sleeping to recover from his excessive use of chakra. Once at the work site, the team is confronted by Zabuza, who has returned for round 2.