On Lelouch

There was a lot to think in this situation. How to get off the island. How that battle went. Where are Black Knights now.

May be he was wondering if he still loves her.

Well ultimately he probably decided to not get her involved in the whole thing. He was like that at that stage of his life.

Well he can try to make her join him, but that would just endanger her without brining much to him or Black Knights in terms of firepower. Actually it would be harder to explain other members why Britannian princess joined them.

Theoretically he could try to use her as an inside spy within Britannia itself. Lelouch as he matured by the end of second season would have done it. However at that stage he was still too young to do something so far fetched with a girl he once loved. 

Also he had not Deithard with him to suggest something like that.

He grows progressively more heartless and utilitarian as series progresses. From being depressed and doubting his cause because its killed Shirley's dad and got her sad. To geassing Nunnally and putting them all in chains for Zero's Requiem.

He himself said that if emotions get in the way he will just get rid of them just before first battle of Tokyo.

And ever since Black Knights betrayed him is kind of became whatever works. Suzaku also became like that just before Schneizel's coup'd etat. 

Events then teamed Lelouch up with Suzaku and he became Emperor.

By that time he became Emperor, he believed in nothing but power of his geass and power of his intelligence. 

From then on he was using this power to shape the world the way he sees fit and people truly became nothing but pawns for him.

He then faked his death to not take any responsibly for brutalities he caused in the process. A lot of people hated him by that point and he could fear assassinations and such. So disappearing in such cunning way was a smart move.

I myself grew up mentally in much the same way. That is why I can relate to Code Geass so strongly. In what other story you can find a character even remotely close to Lelouch.