Disclaimer: I do not own Shingeki no Kyojin or any of its characters. All rights belong to Hajime Isayama.

OOC: this is my first fanfic (and will be a multi-chapter story), so please leave reviews and tell me how I can improve. I'm doing my best to write a LevixPetra story that's not completely AU and doesn't end at Crushing Blow, so I hope you like it. :)

Chapter 1: A Departure Without Goodbyes

He flew through the forest of giant trees, his eyes scanning the foliage for signs of conflict, danger, or Eren. Finding the titan shifter was a simple task, for all Levi had to do was follow the sound of the titan's roars. The difficult part, naturally, was seeing the bodies of the soldiers - his soldiers, who he should have protected - decorating the forest as he traversed through it, their corpses positioned like baubles arranged outside a shop front by a particularly jovial merchant.

One by one, he passed them, and each body sent three knives through his heart - one for the blow of losing them, another for a painful reminder of his past that their corpse gave him and the third for fostering a fear that the rest of his squad would also be deceased. Gunther, Eld, Oluo. One by one, the little sparks of light in his life dimmed. He had told himself that this would not happen; that he would not let this happen. He was wrong.

One, by one, by one… he thought despondently, hoping against hope that he would not see a fourth body. Being humanity's strongest, he refused to show any emotion where he could help it - he knew that it would not do for others to see, and there was no time for grieving while he had a mission to complete - but the next corpse, if it was a corpse, would probably cause him to break down.

That's not true, Levi reminded himself, I'm stronger now than I was the last time this happened. This time, I will not lose my composure. This time… As his fears started to take control of him, he was forced to remember something he'd spent 10 years learning to forget.

—

It was when he had made his first kill. Not a titan kill - a human kill. A murder. Levi was now a murderer, at the tender age of 12. A street fight that his adopted father had managed to get him into through his habit of attracting dangeorus attention had ended with a grown man's death, his blood on Levi's blade.

Oblivious to the somewhat shocked faces of passers by - almost all of whom were involved in shady dealings anyway, and were not usually shocked by this sort of thing (only surprised that the murder had been carried out by someone so young) - Levi looked around for his adoptive father, and, of Kenny, there was no sign.

He began to panic, searching frantically for the man, down alleyways, street corners, and the dens of the criminal underworld that he'd been inducted into. As night fell - or as Levi thought night fell, at least, having access to only a vague sense of time without sunlight in the Underground District - he made his way back to the home he'd shared with Kenny for so long, hoping that he would find his mentor, who meant the world to him even if he was a brutal, violent and sadistic person.

Again, he was disappointed, and found no-one there. However, in the corner of the sparse room in which he used to sleep, he found a crumpled paper note. It read:

Levi,

The fighting skills you demonstrated today impressed me. I have trained you sufficiently so that you can survive, and not die a pathetic death like your mother did. One day, you may find out about her, and about me, and perhaps we may meet again, but for now, I must leave you.

I have my own reasons to do so, and keep most of them to myself. But know this: this is my final lesson to you. The people in you life who you are attached to, who you care about - in other words, those to whom you open up and make yourself vulnerable - will abandon you. They may attempt to kill you, they may die, they may just walk away. One thing is certain in this world, and that is death.

The people you love will leave you without saying goodbye.

That is why I must leave you now, so that you can learn while you are still young what that pain feels like, so that you can remember never to open yourself up to anyone else ever again. Don't make your mistake twice, Levi. Learn from this, and survive.

Regards,

Kenny Ackerman.

Levi didn't fully understand why his adoptive father had done this to him, but his abandonment shook the young boy. He sat down in the abandoned hut that he had called home, and began to cry, his falling tears obscuring Kenny's message. It was symbolic of what was to come, because when it mattered, he failed to see its meaning and heed its advice before it was too late.

—

As he whizzed through the trees, his 3DMG taking him closer and closer towards the distinct sound of Eren's roar, he thought he saw the shadow of someone he once knew lying against a tree trunk. He tried to beg to whatever deity might watch over this cruel world that it had only been a figment of his imagination, but dismissed his own attempt to do so as folly. He knew how to deal with this. After it had happened to him a second time, he would be fully prepared for the deaths of loved ones. Even if he had failed to shut them out once again, he would at least be used to the experience of death.

He would not break - he could not afford to break - when he saw her. He lowered himself down slowly towards Petra. Before he could even recognise her, he was already seeing someone else's face where hers was obscured in the inky blackness of the foliage of the forest.

—

The face was Isabel Magnolia's: his little sister, whom he had vowed - internally, of course - to protect. Farlan's body was lying nearby. The twin impacts of their death did not hit him twice as hard as one would - it hit him exponentially harder. The two crutches he'd grown used to standing on throughout his life had fallen under him, and he hit the cold, hard ground of reality painfully as he stood, devastated, before the vanquished titan.

He had opened himself up to these two, without realising it. He'd combined his efforts with Farlan's to help the impoverished citizens of the Underground District, providing food and shelter to poor souls such as Jan, and, some time later, Isabel had embedded herself deep into their brotherhood, fitting in naturally with the group.

In that district as a child, Levi had done terrible things, but these two had redeemed him, and dragged him back from the abyss of despair and thuggish violence. One day, while stealing supplies with his two closest friends, who were like siblings to him, he realised he'd allowed them to breach the defences of his cold character, and had dismissed the lesson's of Kenny's letter.

The thought of that letter had filled him with bitterness. Since he'd been abandoned by the man, Levi had grown to hate his adoptive father, forming the opinion that his moral outlook was both twisted and ignorant. What did he know of companionship, after all? Who was he to say that Levi's allies would leave him in his hour of need?

Levi, at the time, was confident of his own abilities, but also confident of those of his friends. They'd pull through, Kenny's warning be damned. He would live his life to the full, and he wouldn't let anyone take Farlan, Isabel, and their dreams of surface citizenship away from him.

Due to this, when he set off to kill Erwin, he was the one to abandon them to their fate. He felt guilty about it in the aftermath of their deaths, but the emotion he mainly felt was humiliation. Humiliation, at not being able to defy the laws of life set out in Kenny's twisted world. Humiliation, at realising that Kenny's lessons, though infused by warped morality, were true. Humiliation, at realising that by befriending Isabel and Farlan, he'd made himself vulnerable, and weak.

After crying over their corpses, after digging their graves, after feeling the same emotions - only on a much more severe scale, of course - as the ones he'd felt when Kenny abandoned him, he resolved never to be weak again. He would be strong, humanity's strongest soldier if he could be, and he would follow the code given to him by his adoptive father when he was a young boy. It was how Kenny survived, and it would be how Levi survived.

He would never have to feel regret again about his loved ones leaving his life without saying goodbye.

—

Levi lowered himself, painfully slowly, towards the body of the woman he'd known and loved so dearly. He still didn't really know how she'd managed to fool him, and breach his defences; he still didn't quite understand how she had managed to become more than a close friend, despite his resolution not to let that happen to him ever again.

All that mattered was that Petra had been able to do so. Her radiant smile, which seemed to light up even the darkest of rooms, the grace with which she moved through the air, her wit, sharper than any blade; most of all, the knowledge that they shared the same feelings towards each other. The struggle to resist this was one battle that humanity's strongest soldier could not win.

When he eventually came to terms with his own feelings, after cursing himself for abandoning Kenny's teachings again, he rather enjoyed his defeat, and he thought she did too. His natural ability to delude himself had ensured that, from then on, their lives became more intertwined ever more easily, and, with his own internal walls smashed open by Petra, the others - Oluo, Eld, Gunther and even Hange - rushed through the breach into the complex mix of emotions that was his life.

This time, he had told himself on countless occasions, they could really trust each other; this time, he had found friends that he could rely on no matter the situation. If they died, it would be because they faced a foe so great that the best of humanity could not beat it even if they stood firm together, or so Levi reasoned, and so he would die alongside his comrades. He was ready for a glorious death in battle with his squad, and he speculated that he might even be able to cope with outlasting them, so long as he got the chance to bid them farewell after the fighting was over.

Once again, Kenny was proved right, and Levi was proved wrong. They had died without him - he couldn't help but imagine that they had been alone, afraid and in great pain - and they had left him wordlessly.

He cursed himself internally for failing to live by the code he'd sworn to follow to his grave, for now he would once more feel sadness at someone leaving without saying goodbye.

When he reached her, after glancing around to ensure that no-one was nearby, he allowed himself a mere moment - a few seconds, at most, given the urgent nature of the mission he had to continue with - to check that Petra really was dead.

As he looked down at the body, its head tilted upwards towards him - strong, noble, and yet so frail - he refused to cry. He was humanity's strongest soldier, and he would dishonour the sacrifice made by his comrades today if he did. Tears welled up to his eyes, but stayed there. They would not fall; he knew it.

He was familiar with death now, and so he greeted it like an old acquaintance, without a loud outburst of rage or a cry of grief. How rude, he thought to himself, smiling ruefully at Petra, you've departed without saying farewell. He prepared to fly away on his wings of freedom, which now seemed heavy with a fresh burden of sorrows.

And then, as if death was determined to surprise him despite his familiarity with it, Levi noticed something, and his eyes widened in shock. No, it can't be… he reasoned internally. That's…not…possible…

Petra was still breathing.