Attack on Titan: Shingeki no Kyojin

[Y]

It's been a while. I was really hyped for this show, right?

And they used the solution I'd been suggesting since they introduced the euthanasia plan. "Just cure all the titans". No idea why that required killing 80% of the world first.

Eren wanted to kill most of the non-Paradis population in the world and also destroy their engineering and military capabilities so that after he was dead and the power of the Titans was destroyed, there would temporarily be no capability for a global war. The Titans were already almost getting outmoded as weapons of war, if all he did was erase Titans from existence, the Marleyan Empire just conquers and enslaves the rest of the world.

I'm hearing that the anime ending is significantly different than the manga ending?

A few lines were changed, most notably the omission of the infamous "Thank you, Eren, for becoming a mass murderer for our sakes" line. Instead, Armin now says he believes he and Eren will be together in hell for what they've done. The footprints Eren and Armin are sitting in were filled with water (and then blood) in the show.

The biggest change is in the credits montage. In the original manga ending, the series ends with Mikasa sitting by the tree. The stuff with the world moving on and the city being bombed was added in the volume release. Crucially, in the comic, it's unclear when the apocalyptic war is taking place - we see bombers and modern apartment buildings, but given that presumably all the engineering knowledge from the outside world survived and they were already in the 1940s or so (with exceptions like the impossibly advanced 3D Maneuvering Gear) it's entirely possible this was only a generation or two later. This maintains ambiguity over whether Eren's plan worked or not. It could be the "war of reprisal" he was worried about happened after all, or it could just be an unrelated conflict in humanity's endless cycle of war.

In the show, the city advances into some kind of futuristic sci-fi cityscape. This almost certainly means that the "war of reprisal" didn't happen and that it was just an inevitable global war, as it would presumably take centuries before they were able to live in the Blade Runner society. So for my read the show leans much heavier on "Eren and the gang of Paradis Island won at a heavy cost" rather than leaving it ambiguous.

What I still don't get: are we supposed to believe that Eren only acted/pretended all the stuff he did in the beginning of the show while in truth following his big plan? So when he says he sent that one titan to eat his mom inst9oc Bertholt, was young Eren's crying and wish to save her all fake? Did he pretend to be bad at using the gear during training camp? Did he pretend not to know that Annie is the female titan? And so on?

Eren can supposedly virtualize his memories, and "future memories" through the Paths, but this is not retroactive. He only obtained this ability when he touched Historia. It doesn't percolate backwards in time to earlier iterations of his consciousness.