"Zero Visibility: The Sharingan Shatters" (視界ゼロの戦い・写輪眼崩し, Shikai Zero no Tatakai - Sharingan Kuzushi) is episode 15 of the original Naruto anime.
Kakashi reveals his Sharingan to Zabuza once again, but Zabuza claims he won't be fooled by the same jutsu twice. He explains that Haku observed Kakashi's Sharingan and discovered a way to counter it. Zabuza says that Haku's jutsu even surpasses his own. Inside the Demonic Mirroring Ice Crystals, Naruto and Sasuke struggle against Haku's superior speed. After watching Haku counter Naruto's shadow clones, Sasuke begins to see Haku's movements. He uses Fire Release: Great Fireball Technique and manages to hit Haku, but Haku says his ice is stronger than Sasuke's fire.
Zabuza uses his Hiding in Mist Technique to negate Kakashi's Sharingan and claims that the next time Kakashi sees him will be as Kakashi dies by his hand. Zabuza vanishes, leaving Kakashi to anticipate his opponent's next move. Kakashi finally realises that Zabuza will strike at Tazuna and Sakura and rushes to intercept the attack. Zabuza makes his move, and Sakura screams.