We looked it up and it's apparently just an alternate world where titans didn't destroy the wall. Basically telling Mikasa that Eren is guaranteed to die regardless which helped her keep focused in ep 5 of season 1. (according to the internet lol)
TKOhhh
2025-07-13 22:33:57 +0000 UTC
Yeah that was NOT the future.
That was Mikasa going into her own headspace to create an imaginary world where she'd hoped that she and Eren could be together. Where life would be different from her reality. However even in this imaginary world Eren will always remain Eren.
I think the mirror man, IMHO, was herself telling her to kill off her own innocence, like she did in the cabin back in the real world, to be with Eren. But said, Eren being Eren, he ends up getting himself killed in a hot air balloon accident in this imaginary world to save Armin who is left behind and emotionally broken about his death as well.