Kurenai's Top Secret Mission: The Promise with the Third Hokage

is episode 205 of the original Naruto anime.

Synopsis
As Kurenai attempts to escape with Yakumo, Naruto, Sakura, the members of Team 8 and Might Guy come to their assistance and defeat the enemy. Kurenai and Yakumo reveal that Yakumo was entrusted to Kurenai as her student, as while she was unable to fight, she was a talented genjutsu user. However, Kurenai sealed away her abilities, and Yakumo reveals that she did so under the order of the Third Hokage.