Naruto Chapter 385: The Secret of the Mangekyou

Summary: Sasuke asks Itachi who the third Mangekyou Sharingan user is, because he figured he was Itachi's accomplice in killing the Uchiha, and thus next on his hit list. Itachi tells him it's Uchiha Madara, his mentor, and an immortal who was the first to awaken the Mangekyou Sharingan. It's true power is the power to tame the nine-tailed fox, but the price is blindness. (Read 385 here)

SnowyOwl Says:

I was pleasantly surprised that Sasuke asked an unexpected question. It was forward-looking and action-oriented (this is what I'll do next) vs. what I expected, (i.e. Why'd you do it?) which would have been backwards-looking, as Sasuke has been this entire time. Granted, his mission is rooted in the past, but at least his mind isn't trapped there. The question also dispelled any theories that Sasuke had planned on dying with his brother (end of mission).

Madara = immortal, confirmed. But it still doesn't rule out the possibility that Madara is inhabiting Obito's (dead) body. Ew. It actually makes a lot of sense that Itachi had a mentor who gave him direction, nurture and validate his sense of superiority, and helped extinguish the Uchiha. A lot more sense than 'Itachi just is,' or Itachi just decided to,' anyway.

For an in-depth discussion about Itachi's philosophy and personality, go read zapenstap's Itachi Analysis Essay. The ideas there are consistent with Itachi's motives, which are revealed in the next chapter if the spoilers prove true.

By the way, don't read spoilers. They...spoil stuff.

On a side note, yes Itachi may be going blind, but at least his eyes make funny noises. Swuuu!