"The Key…!!" (鍵…!!, Kagi…!!) is chapter 94 of the original Naruto manga.
Worried about what Orochimaru may be planning, the Third Hokage visits the Hokage Rock to think. There he finds his grandson, Konohamaru's, Academy class learning about the four Hokage. When they doubt his qualifications as Hokage given his age, the Third assures them that he would give his life to protect each and every one of them, just as they would their own friends and family. Meanwhile, with Naruto's progress with the Summoning Technique going too slowly, Jiraiya takes drastic measures. He throws Naruto into a deep chasm, depending on Naruto reflexively using the Nine-Tails' chakra to save himself.