Full summary: When he finally finds him, Eren doesn't remember but Levi does and it hurts more than he can explain to be so close yet so far away from him. He could reach out and physically touch him but there will always be a distance between them. And even though Eren doesn't remember, Levi sees the past reflected in all the small things; in the brown of Eren's favorite belt, in the slight obsession with wing patterns, in the craving for freedom, the way he unconsiously bites his hand out of frustration, in the perfect shade of green Eren is obsessed with, but mostly in the way Eren looks at him when he thinks he can't see him. Every little thing is a painful reminder that despite all that, Eren doesn't remember.

Or:

A reincarnation story which Levi is painfully aware of their previous life, Eren isn't, and the world is still a cruel place after so many years.

Levi starts dreaming, remembering, when he's only a child.

The dreams were nice, almost like a secret world only he knew about. He would close his eyes and dream of a city surrounded by high walls he's never seen, of flying through the sky, of riding horses on the outskirts of an empty field, of living in various places he doesn't recognize but feel right, almost like home. He didn't really remember them, too young to understand their importance but "it didn't matter because they were only dreams after all, right?"

But as he grew up he became more aware of them, they lingered in the back of his head when he woke up and they were the first things he saw when he fell asleep. The dreams continued, increased in frequency it seemed. He didn't understand seeing all these places he didn't remember visiting but he felt like he needed to know where they were from. He would wake up with names burning in his throat and images flashing behind closed eyes. It left him frustrated and somehow disappointed in himself. "It doesn't matter, they're only dreams" he tried to tell himself but it didn't help, it didn't calm the uneasiness he felt when he couldn't remember. Needless to say, Levi didn't like having those dreams anymore.

One day Levi finally asked his parents about his dreams, hoping they knew more.

"Where is the city surrounded by walls? I... I need to go there but I don't remember where it is."

Levi's parents were surprised by the sudden question. When they asked him "what city", Levi told them about his dreams, about the places he saw and the things he did in his dream world. It was almost unsettling how much details he could tell them. It also was the most his parents had heard their son talk and if they were honest, they were a little worried. Levi had always been a quiet and rather introvert child but when he spoke with such passion about "the city surrounded by walls", they couldn't help but wonder if he wasn't slowly immersing himself in a fantasy world to drive out the loneliness. Levi might be young but he understood the look of worry in their eyes. He quietly tells them "nevermind, they're only dreams" and returns to his room, wondering if the dreams were something bad.

He never talked about them after that one time.

By the time Levi graduates from high school he immediately moves out, using the start of university as excuse to leave the house. He really does care for his parents but he can't help but feel like a stranger in his own home at times. He blames the dreams. By then he remembers every single detail of the city surrounded by walls, he recognizes the people, soldiers, around him and it scares him how well he remembers. He remembers the people in his dreams better than his high school classmates and somehow his parents don't feel as real or close as those people and it makes him uncomfortable, guilty for feeling that way but he can't help it. Levi wonders when he started accepting the dreams as something more than just dreams but he can't remember. Maybe he has always felt that way.

In his childhood his dreams were filled with snippets of what seemed a long adventure, one about a city surrounded by walls. The snippets were peaceful and about calm or pretty moments of that world, they were nice, relaxing almost. But when he got older he saw more, remembered more.

The first time he dreams about them, titans, -human like creatures whom are snapping and eating the screaming soldiers around him- he runs to the bathroom to throw up until there's nothing left but he can't help it, he keeps remembering the sight of crushed limbs and blood and the smell of death. He can't stop shivering and when he closes his eyes for only a few seconds the horrible images almost make him throw up again. He keeps washing his hands until they're raw but he can't scrub off the feeling of warm blood splattering on them.

He sits down and leans back against the cold bathroom tiles, trying to tell himself that he's safe, that he's in his own apartment and there are no titans here. He just sits there in a daze, trying to process what the hell he just had seen, what those dreams actually meant.

When he somehow manages to fall asleep in a restless sleep it's like a switch has been flipped and everything, every little detail of his previous life forces itself into his head. He dreams about the underground, about the Survey Corps, about Erwin, Hanji, his squad, about his first time outside those walls, about killing titans and about Eren.

When he opens his eyes he feels a lifetime older and is crushed by a hollow, empty feeling, wondering why he hasn't met the others in this lifetime -what if he never will- and asks himself why, why did he have to remember, why?

The next day, as if fate is mocking him, he finally meets Erwin.