Code Geass: Lelouch of the Rebellion R2

[enkoujin]

I thought Lelouch's purpose of fighting was so that Japan could be free and him and Nunnally can live happily.

It was.

Now he wants to takeover the world just because he thinks Nunnally is dead?

Well, after his conversation with Charles and Marianne, he wanted to deny their world, and with Charles revealing his plan that Schneizel will be trying to change the world, Lelouch didn't want that. So to stop one person from seizing a chance at changing a world you wouldn't like, why not grab it for yourself?

So as mentioned in gg's translations, he's gone on with a plan, "Requiem of Zero", to shape the world into the ideal world both Euphemia and what he thought Nunally had wanted. After all, it was partly, Lelouch's fault for both their deaths. This atonement Lelouch must have pledged had probably brought Suzaku and himself closer together to working aside one another. He followed Suzaku's way of "changing the system from the inside" as well as his own way of "destroying everything, and recreating anew".

And why is Nunnally so quick to become their enemy?

Schneizel, with his clever diplomacy, negotiation, and persuasion skills, who wouldn't become Lelouch's enemy under his hypnotic speeches? If he could turn the tables on Lelouch with Lelouch's high-tier staff, why couldn't he do it with his own blind half-sister? A month has passed since the FLEIJA warhead in Japan, with Nunally surviving it, and within that certain period, Schneizel probably bombarded Nunally with what was happening behind Nunally's back. The fact that Nunally had been betrayed nearly her whole life, and lied to by her closest friend (Suzaku) and her brother (Lelouch) influenced her decisions and viewpoints.

And wtf is this whole Lelouch is going to kill a lot of people for? Why is that necessary? If he's the emperor, why not just declare Area 11/Japan free?

Not sure which scene you're talking about. After Lelouch broke down the aristocratic system of Britannia where the elite had ruled, some aristocrats that weren't geass'd lost all their wealth and power. Without their power, why wouldn't these people fight back for it? So there had to be repressions on these rebellious people, otherwise there will be a shift back to the monarchy-aristocratic state.

If you're talking about the UN meeting, Lelouch killed "those people" (the soldiers/bodyguards) because they could have taken him down, as if Sumeragi wasn't already cynical enough of his actions. Then, there's the invasion of Britannian troops into Japan. Since Lelouch already became the emperor of Britannia, and the OBK had made no quick attempts at diplomacy to establish ties with the new Britannia, Lelouch might have thought of them as a threat. Now, since the UN "employs" the OBK as their main military organization, if Lelouch could take down the OBK, he can rule the world, as there would be no "clear" enemy at his standing.

Plus, he called off the colonization of Japan already. It's already liberated, but it was part of all his plan for everyone to have a better view of Lelouch (which definitely worked, as exemplified by the people in Japan cheering for him), which allowed Lelouch to commence his operation to rule the world.

The reason Schneizel is even letting Lelouch take over the world right now is that he's playing the "bait out" card. He's letting Lelouch having everything, and once he's at the top, Schneizel would swoop in and take everything back, which leaves Lelouch in a most humiliating defeat - usually a plot device of "a fate worst than death". Best example I could think of would be that of the orphaned boy-Carter Pewterschmidt scene of Family Guy where they filled out the paperwork to adopt an orphan boy and taunted the orphaned boy with gifts inside the car before driving off, leaving the orphaned boy just devastated.