Erwin was never interested in Omegas - not that they aren't good people or anything. He's met many females who have flung themselves onto him at a single whiff of his scent, and all have been perfectly fine women, but he never took an interest.
Betas, on the other hand, have mainly been the subject of Erwin's affections, the most notable being Nile's Marie. Maybe it was because Betas bring some sense of normalcy to this chaotic and tragic world, or maybe it was because he didn't like his relationships determined by biology or a smell.
Erwin never thought too much about it. Why bother with something so trivial when there are flesh eating monsters and a corrupt government trying to cover it up?
And then Levi entered his life, and he fell for the Omega harder than anybody else, Marie included.
He knew Levi was an Omega, he could smell it through even the dirt of the Underground, but for some reason it didn't matter; his graceful and talented use of 3DMG, his determination to defy Erwin with every ounce of his being, and the unspoken care he had for his two friends, set him apart from anybody he'd ever met. No scent or biology involved; just Levi.
Even when Levi hated him, Erwin loved him.
And even now – especially now – Erwin still loves him, with every pulse of ruthless heart.
With Levi's body in his bed, Erwin's days pass peacefully (even with an expedition looming). And despite going against every single ounce of Erwin's logic, he wishes that they could stay like this forever.
One night, Levi's distressed scent wakes Erwin to see the Omega pressed into the corner between the bed and wall, his body thrashing and shaking in a frightful trance.
"Levi," Erwin says, placing his hands on Levi's shoulders.
"Get away from me!" Levi screams, swatting Erwin's hands away.
"Okay," Erwin says calmly, moving away. "I'm not going to hurt you, Levi. It's me, Erwin, remember?"
Levi's body continues to shake, but his head is dipped, hair covering what is probably a tear stained face. Erwin wonders what Levi is thinking right now, but knows that he shouldn't push it. He's let Levi go at his own pace for this entire time, and he isn't about to start pushing him now.
But still, he can't help the urge to bundle Levi into his arms, nuzzle his neck and tell him that everything is going to be okay. He can't protect Levi outside the walls, but he can at least try to protect Levi right here in this room. It makes Erwin's mind itch with disgust that he can't help Levi.
"Levi," Erwin says softly, "I'm right here if you need me… "
He hears two broken sniffs, before Levi lunges for his body, arms wrapped tightly around Erwin's stomach. Levi doesn't make any noise or movement, and simply presses his body against Erwin's own.
"There we go," Erwin whispers. "It's alright, I have you."
Erwin knows that any vow to protect Levi would be pointless, because there's no way that he could ever manage to protect Levi from this world without any doubt. Even disregarding the titans, he knows there's hell inside the walls as well. Erwin couldn't do anything to save his father, and if the same people got a hold of Levi, he doesn't know what could happen.
So he makes a silent vow, heard only by himself, to do whatever in his power to protect Levi from his inner demons. He should be able to do that much.
It's a while before Levi's shaking recedes, and as he pulls away, Erwin notices that his eyes are rimmed red.
"Thanks," Levi mutters.
"Do you… want to talk about it?" Erwin asks gently.
Levi pauses. "No," he says, "I don't want to talk about it. But I think I should. If we want this… thing to work out between us, I think you should know."
Erwin nods. Although he has a fair idea about what Levi is going to say, he prepares himself for anything. "Whenever you're ready."
Levi takes a deep breath.
"I didn't always live in the Underground, and for most of my childhood I lived with this- well, I don't think I could call him a man, because he was more like a monster, but I lived with him and he trained me in 3DMG and hand to hand combat. He thought I was an Alpha, my physical attributes at the time all pointed in that direction, so I was raised as an Alpha." Levi stops to take another deep breath before continuing, "Until I started smelling like an Omega. I became nothing more than an object- a plaything for him to push around and abuse more than he already had."
Erwin bites the inside of his lip to stop himself from getting angry. Levi's words set his nerves on fire, need to protect his Omega pulsing in his veins, but he knows he needs to be calm. For Levi.
"When I started to go into heat, he started… started sexually abusing me. I knew then I had to run away." Levi's voice cracks. "So I did. I ran. Fought my way to the underground, got some cheap suppressants, started taking them, found Isabel and Farlen and the rest you know, of course."
Erwin nods, unsure of whether to reach out and comfort Levi yet.
"So that's it. Now you know how fucked up I am."
"You're not fucked up," Erwin insists. "The titans? The Military Police? The monarchy? They're all fucked up. You're one of the strongest people I know."
Levi shakes his head, avoiding eye contact. "Stop saying shit like that."
"No," Erwin says. "Not many people can stomach the life we live, but you do. I think that makes you incredibly strong, not just physically, but mentally."
Levi stays silent, and Erwin reaches out to grab Levi's hand. He entwines their fingers like he's done several times over the past couple of days and gently pulls Levi closer to his body. They stare at each other for several minutes in a rare of moment of serene calm. There's no longing or lust or animal instinct; it's just them, like it's always been, two souls trusting in each other.
Levi buries his face in Erwin's neck and inhales briefly at his scent gland, sighing in comfort. "Thank you."
"I love you, Levi," Erwin says, speaking the words like they're a prayer.
Levi snorts, "You're so dorky."
He probably is, but Erwin doesn't have the capacity to care, not when it comes to Levi.
Levi trails his slender fingers down the side of Erwin's neck, and Erwin starts to think that maybe he shouldn't have said that so soon, but then-
"I love you too… but it doesn't mean much to me. Trust, on the other hand, is extremely important to me, and I trust you more than I trust anybody else in this shitty world. I hope you know that."
Erwin genuinely believes that he doesn't deserve Levi's trust; he never did, not after forcing him and his friends into the Survey Corps, which basically signed their death certificates. But somehow, he's earned it, and now that he has it, he'll protect it like the most fragile of glass.
He presses a soft kiss onto Levi's lips, stroking his hair gently, "I know."