"The End of Youthful Days" (碧き日の終わり, Aoki Hi no Owari, Viz: The End to Blue Days) is chapter 667 of the original Naruto manga.
Finally arriving to Sasuke's side, Orochimaru and Taka discover that the mysterious man is Kabuto — who was finally able to break Itachi's Izanami by finding his true self. Using his medical ninjutsu along with his knowledge about Hashirama's cells, Kabuto begins treating Sasuke under the instruction of Tobirama. On Madara's side, Kakashi reassures his sensei that he was all right before the Fourth reiterates that only taijutsu and senjutsu attacks would work on the Ten-Tails' jinchūriki, but that his skills with senjutsu are limited. Guy opens the seventh gate and attacks Madara with a powerful punch, but to no avail. With Madara trying to kill Guy, Kakashi launches one of Minato's kunai to warp the black orb away, but Guy is instead saved by Rock Lee, who brings him to their comrades' side. As the shinobi wonder about how to deal with their enemy, Guy tells Kakashi that it is time for him to become a crimson beast by opening the eighth gate, which will eventually result in his death.