Her and Captain Levi have always shared a mutual demeanor. They both were collected and structured like machines in battle. They both shared a similar past, with similar inner awakenings that left them prime for their duties to the capital. But, if she were honest, she had never considered their developments outside of the line of duty. And neither had anyone else for that matter.
She loved Eren more than she could ever love herself. He was her childhood savior, her companion, the lost love of her life. But Levi held a different piece of her. A piece she never thought she needed until he approached her that night. He gave her security, ease, and understanding. Their blood line was as similar as the rest of the humans within the walls. Their connection, separated by lines and lines of mistresses and fourth cousins. But it was their understanding of themselves, of what was passed on to them, that made them stick to each other.
Levi was something she needed.
As he lay, napping while she sat and gazed, she pictured the gruesome memories they had both shared. Loved ones dying. Crumbling consciences as soldiers gave up their lives under the pretense of his and her best judgments.
These moments of peace gave them the strength to face new days. New days under the rule of a new empire. New days laced with personal problems, rather than the struggle to survive. New days of trauma, regret, and sadness from previous years of hardship.
It had been a year. One whole year since Eren had given up his life to save humanity. To save her, Armin, Jean, Sasha, Hanji, the outside world, everything anyone ever knew and didn't yet know. She never thought she would be able to go on. It was on the fifth night of her severe mourning the loss of Eren did Captain Levi enter her room.
He sat across from her and took her hand. Petra was who he had talked about. How he was considering marrying her before he inevitably saw her body crushed by a ruthless Titan. How Petra's blood sprayed on his face, expelling the same warmth that her body had once given him. That it was the one time that he didn't consider ever cleaning his face. He confessed to Mikasa on this night, that Petra had been the only one he deeply cared for, just like Eren to herself.
"I beg of you to mourn and then keep living," he said to her, "Because right now, your life is why mine continues."
She took his words and eventually understood. Levi's purpose in this world had diminished with the Titans. And in a sense, so had hers. They both fought for the sake of humanity and lived for the ones they loved more than anything. Now, humanity no longer needed them, and their loved ones had since passed. They were alone, miserably bonded by tragedy and blood, her lost cousin and herself.
She understood. She knew she would never live a normal life. That much was obvious from the day she saw her parents die, from the day she killed someone for the first time. She would never be truly happy. Neither would Levi. But they could both find something worth getting up for every day...
In the strength of family.
And maybe, one day, the good times and good things it created would deafen their years of bloodshed.
Mikasa carefully brushed the stray hairs from his sleeping face and she fell into sadness. Pain sliced through her thoughts. But only for a moment this morning. For, in front of her she had someone who had the ability to drown out her toxic memories.
Things do change. And things do grow from nothing. And as he opened his eyes to hers, past nightmares suddenly turning into blissful realizations, she smiled at him with all the happiness she had been saving.
He reciprocated, and lifted his body to say, "Let's get moving, we've got a lot to do."
She smiled and stood with him.
This world was theirs.