Two Heartbeats: Kabuto's Trap

is episode 140 of the original Naruto anime.

Synopsis
Naruto arrives in the nick of time to save Sakura, but not before Kabuto tells her that Sasuke is dead. Naruto tells her not to believe him and a battle ensues. Naruto defeats him with the Rasengan, but Kabuto traps him in some chakra threads that connect their hearts; if Kabuto's stops, so will Naruto's. As Kabuto attempts to kill himself to end Naruto's life, Sakura tries to free him. Sasame arrives and gives Sakura a special Fuma Clan tag to help save Naruto, only to find out that the Kabuto they fought is actually Kagero, who dies suggesting that Sasame should not know what Arashi has become. They finally find Arashi, who has been disguised as Orochimaru, who reveals that he has indeed changed.