I don't own Shingeki no Kyojin.
AU notifications beyond the obvious: Mikasa got further out of sight during her suicidal run during the invasion of Trost and Armin was a little slow in finding her after she fell.
Also, for the record, felt the whole "not enough gas to climb the wall" was a little contrived, seeing as they certainly had an awful lot of rope, and 150 feet isn't all that far considering how physically fit they are, but I'll play it according to canon. Wouldn't be the first time in the world a group of people under threat of death failed to realize the obvious.
Chapter One:
'Where am I?' I shifted my foot from the smoke as the heat impinged on my swirling thoughts. I stumbled back, body betraying me, and the world shook. My back crashed against a wall, 'no, a building,' and tiny bricks skittered across the ground below me. I peered into the smoke, now realizing the impossible truth: It was a titan, and yet it was little larger than me. I stood, ever slowly, watching with restrained horror as I rose higher and higher. My eyes reached level with the highest window of the apartment building. How tall did that make me? Twelve, maybe thirteen meters?
That's when I saw her. So tiny, delicate even, though I remembered any number of times she had sent me spinning to the floor in a spar. Clutching a broken blade she stood alone in the ruined street. "Mikasa?" My voice rumbled, low and thunderous, but somehow distinctly feminine. I looked down, somehow accomplishing the impossible in making myself even more shocked than before. Raven-black hair swung at the edges of my eyes, just like Mikasa's. Swinging my face back to the window fast enough to hurt my neck I peered at it's surface, desperate to capture every detail. My fingers trailed across my cheeks, testing the vision that my eyes could not believe. 'This is me?' But it wasn't my face at all, it was hers.
"Wh-what happened to me? Where's Armin?" The last thing I could remember was... was jumping into a titan's mouth to save him. He'd bitten off my arm, so why wasn't I dead? I should be dead, shouldn't I? People didn't just wake up thirteen meters tall looking like their best friend after being swallowed by a giant. I didn't even look like a titan. That, at least, might have some logic behind it. Might hold the secret of how titans actually produced. Instead, I looked human. Just... very, very tall. My knuckles ached, as if I had punched something with all my strength. Had I killed that titan with just my fists during some sort of blind rage?
"Eren?" Her voice was so soft I could barely hear it.
"Mikasa, what happened to me?" I bent towards her as I spoke, but recoiled as I saw a flash of fear contort her face. She recovered almost instantaneously, strong as always.
"There's no time for this now. We've been cut off from our resupply point. We don't have enough gas to climb the wall and the trainees I sent to take back the headquarters will be slaughtered without my help. You need to carry me."
"R-right." I didn't dare grab her for fear of crushing her, but instead lowered my hand to the ground, palm up. Athletically springing on top, she grabbed ahold of my thumb that was now about the same size as her thigh. Might right hand clutched at roofs as I started us on our way, half shattering them as I pulled at them for balance. "I think I'm starting to get the hang of this." My steps grew more sure, and soon I wasn't walking but running, ground flying beneath us.
"You had better. We won't get inside without a fight." That was understating things. I was close enough now to see a depressingly small group of fighters swing into the top floor of HQ, but surrounding the building was a group of titans of all sizes. "Hey, stop for a second." I halted, stumbling slightly as I tried to account for the changes in momentum and my center of gravity. "Grab that. If you're going to walk around with my body I'd prefer that you show at least a little modesty." She gave a hesitant smile, obviously as disturbed with my transformation as I was. I grabbed the two giant flags from the mayor's mansion, tying them around myself with a blush. I grabbed the flagpole too for good measure. Considering the state of my knuckles, I'd rather not beat on too many more barehanded if I could help it.
The stop for something as simple as modest could be considered criminal, given the circumstances, but we were both far from being calm. The clothing, as simple as it was, was a touch of normality to keep us both sane. I looked different enough from the titans that other humans might hesitate before attacking me, but I was obviously not human. Still, I didn't have the hideously stretched mouth of normal titans, though like them I felt somewhat lighter than I should if I were made entirely from flesh and bone. My knuckles, too, were already visibly healing, though at nowhere near the rate of a true titan.
Apparently the other titans felt I was different as well, as several stopped heading for the HQ castle in favor of chasing me. "Dodge them," shouted Mikasa, struggling to be heard. "I need to get inside before anything else." It was easier said than done. The three to five meter class were little difficulty, as they hardly came up to my knees. They couldn't come close to matching my speed, and even in the mass of them their small arms did little to detain me. The seven meter class was more worrisome. The size of children – ugly, apelike, flesh-eating children – they had enough mass that one good grab could send me sprawling. I leaped upwards over a trio of them, feet coming level with the roofs as Mikasa held on for dear life. It was during my brief flight that I noticed the next obstacle.
I ducked under his arm as he swung at me, but another stood right behind him, blocking my way. Both were a full three meters taller taller than me with limbs as thick as my waist, their features a brutal caricature of humanity. The horde of smaller titans was swiftly approaching my back, but suddenly I found myself wondrously, gloriously unafraid. This was what I had trained for, this was the threat I'd dedicated my life to eradicating. It didn't matter if I was a twelve meter tall girl, so long as it helped me be free, to break free of the gilded cage that had trapped humanity for a hundred years.
"Hold on tight." I jumped upwards, rolling up and over the building to the right of us. Tiles shattered from my passage, prickling against my skin. I had no time to spare for pain, but my gambit had worked. The way was clear, and with a renewed burst of speed I sprinted for the castle, titans howling their outrage behind me.
"Look out!" I spun, flag pole sweeping out to catch the deviant flying through the air at me. It was the same fifteen meter monster that had eaten Thomas. The pole was just enough to send him off course to smash through a building, but he took my improvised weapon with him.
"Damnit!." Fury rose within me, my free hand clenching into a fist as I considered rushing into the crushed building to finish him off. To my regret, there was no time. It looked like every titan in the town was coming after me now, so I was forced to grit my teeth and keep going. Two more titans a little larger than me were digging their hands into the tower, but fortunately they were too distracted to go for me at the moment. Climbing onto the first level of the castle I reached up to place Mikasa in the highest window.
"Eren, distract them if you can for ten minutes. I'll be back out soon to help you."
"Right." She disappeared in a flash, headed to places she could not follow. I hoped she faced less of an opposition inside than I did out here.
Jumping down, the shock wave sent small titans stumbling. I took the opportunity to punt each of them flying as they rose to their feet. One particularly brutal kick that left my foot stinging was just enough to rip off a 7-meter's head. I darted forward to give him the coup de grace but a pair of his fellows drove me back. "This isn't going to work." Already the one I had felled was regenerating, and the 15-meter monstrosities now arriving were stronger than I was, even if I had an advantage in speed. I could take one of them on, maybe two, but if I stayed here much longer I'd be overwhelmed in short order.
Looking around me to guard against being cornered I saw it, a speck of yellow against the red roofs. "Armin?"
Shingeki is absolutely amazing, it's a shame its plotline is so perfect that it's difficult to write fanfics of. Harry Potter on the other hand, well, I think anyone sane admits that those books had more holes than the bogs outside Mordor.