So i'll ride the band wagon and argue that:
Lelouch is alive
why?
Lelouch was a stage master who planned ahead of everything. Both seasons have continuously demonstrated this fact. Zero's requiem was one such plan so that its conclusion, his death by zero, was not done by impulse.
The main goal of the plan was to have his emperor persona die after gathering the focus of hate of the world. Zero would then be considered a hero and at a prime position to once again guide people into peace.
My initial reaction after seeing the episode was where in this plan did it require for lelouch himself to die? Wouldn't faking his death and simply disappearing be equally effective? Who or what prevents this scenario from happening?
Who?
The big three CC, Lelouch and Suzaku were conspirators in this plan. The idea that Lelouch should really die would have to come from them.
Lelouch: He made his stand about how he values his life when he rejected Charles' plan:
"I want a tomorrow " so suicide no matter how guilty he feels should not be his answer.
CC : She refused Charles when she found someone who finally understood/loved her. Naturally in this path she would also want lelouch to live to be with her as she
lives out her immortality
Being the last geass user, Lelouch is also her only way out of immortality so having him die on her like that is something she would consent to - alternative would be to eventually find some poor ambitious sap to trick into obtaining geass again.
Suzaku: who wanted revenge for euphemia was portrayed as someone who understood (after the events of killing 35million nins) that practicality must overcome emotion to create a better world.
This said, his alliance with lelouch was
based on trust (that he needed lelouch to realize his goals) and
not on the condition that he gets to kill him.
By the end of the series i felt that his two conspirators truly cared about lelouch so that even if they were aware that he won't die himself it was still a great tragedy that he would be remembered as a villian by so many and no longer able to be with those he loved the most (nunnaly) thereby explaining why they were crying during the realization of zero's requiem.
What?
Cornelia, her knight, Nunnaly and many others survived situtations that people thought should have killed them with only small hints showing how these were possible. Surely if it was not suicide then lelouch, Suzaku and CC could have come up with something in 2months,. That and this particular sunrise show really seems to want people to live
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