So, here we are: Annie is very out-in-the-open about being the Female Titan, but it doesn’t change her plan: to capture Eren. Why is a question that remains unclear: if she wanted to deprive the humans of a weapon against other Titans, she could just kill him, like she killed Hange’s two test subjects. She’s been very careful to keep Eren alive.
This episode flashes back to the planning of Annie’s trap, along with an Eren who won’t accept that Annie is the Titan, no matter how much circumstantial evidence Armin and Mikasa come up with to try to convince him. Back in the present, on the run in tunnels they thought would be safe but are actually quite the opposite, Eren finds out just how devastating the inability to give nothing up can be.
With no resolve whatsoever to kill or even harm Annie anymore, he can’t transform into a Titan when he needs to the most, no matter how much he may want to transform, it can only be for a purpose, and his heart just isn’t in it. He must’ve thought back to all those fun pillow fights with Annie back during their cadet days (which we never saw):
Eren’s problem, then, isn’t that he doesn’t believe Annie is the Female Titan; that much is clear at this point, now that he notices the resemblance both in their appearance and fighting style (along with the fact she transformed right in front of him).
But while Eren can’t give up on Annie as a human and a friend, Annie can give up everything, which is why she can transform any time she likes and kill with abandon. Even Armin and Mikasa put their lives on the line in a gambit to allow Eren to escape. As Mikasa says, it’s a cruel world. Shit like this goes down, and you can’t worry about what’s right, or you’re dead.
Mikasa and Armin successfully lure Annie into a trap by Hange, but I knew from the pittance of arresting cables that she wouldn’t be held for long…It might’ve served Hange to fully incapacitate Annie before gloating about catching her then describing what she’s going to do with her (everything she can).
But this isn’t about whether the Scout Regiment can catch Annie, or whether Armin and MIkasa and Jean or Erwin and Levi and Hange can somehow pull something off without Eren in the picture.
The only thing that’s going to bring Annie down is Eren in Titan form. And to become a Titan, he’s going to have to convince himself to give up on the idea of Annie as a friend to be cherished, but an enemy to be killed without hesitation.
Buried by rubble and with a stick of wood in his chest, Eren thinks back to all of the people lost before his eyes and/or in front of him, starting with his mother being eaten years ago in Shiganshina where it all started. This isn’t time to be worried about his soul, or about not being to walk away having lost nothing. This is about putting everything—even his humanity—on the line, and getting the job done.