[double posting, originally posted on AO3 under the AkuAtsu tag]
Well, it's my first fic for the fandom, and it's a Soulmate AU! I thought the idea was original enough (but I have no clue if anyone else has ever thought it up. In any case, before I start rambling, I hope you enjoy!

Akutagawa was drifting asleep when he felt an itch on his wrist. He frowned and scratched at it furiously, hoping it wasn't the bed bugs. Next to him, Gin shifted in her sleep, her eyebrows scrunched tight. When he reached out to hold his sister, the dark scribbles he saw on his wrist stopped him.

It couldn't be.

Squinting in the dark, he could barely make out the words inked on his skin; so dark it seemed to blotch.

'I did it.'

A violent cough ran through his body and he stared at his hand, wide-eyed.

At nine years old, Akutagawa discovered, to his horror, that he did have a soulmate. And this soulmate of his told lies often.

By the time he was fifteen, Akutagawa only had Gin left. The other children they had known in the slums were taken by traffickers. They had wandered around for days, starving. His poor constitution had rendered him unable to move on most days, and despite his protests, it was Gin who ran about pickpocketing, amassing enough money to barely keep them alive. If this was the kind of life they were destined to live, Akutagawa wondered if it was even worth living at all.

Summer came and the sweltering heat did nothing to improve his condition. Gin sat next to him with an almost glazed expression on her face. Akutagawa struggled to stand, and it was then that he saw writings on his upper arm. It was even darker than the first time his soulmate's lies had appeared on his skin. And the darker the lie, he had come to learn, the more serious the lie.

'The Headmaster is... the best.'

He couldn't make head or tail of it, and he wondered if the boy was some judgmental prat. His thoughts on his soulmate didn't linger long when someone poked his head into the alleyway.

Akutagawa took a wobbling step forward, his throat tightening. He couldn't even muster the strength to lift his arms into a defensive position. Every step he took, his lungs burned and his body groaned in protest.

"Hey, hey, calm down!" The man smiling widely at him looked like a goof, save for the bizarre bandages running up his hands. "I heard there's a pair of ruffians causing trouble in the area. I've got an offer, and I'm absolutely positive you'll love it."

Akutagawa stared at the man, incredulous. "What?"

When Atsushi was seven, he was pushed against a wall and made to hold still while the sneering older boy waved a pair of scissors in the air. He flinched when he heard the definite snip-snip and the soft whoosh of air as locks of his hair fell to the ground.

"Now nobody will mistake you for a girl, Nakajima!" the boy howled with laughter, and Atsushi couldn't help but watch as the glinting metal brushed against the last shoulder-length lock of his grey hair.

"What's going on?"

The boys stepped back, and the bully shoved the scissors into Atsushi's trembling hands. He snarled and gripped the younger boy's shoulder with enough force to bruise. "If the Headmaster asks who did it, what're you going to say?"

Atsushi swallowed. When he didn't answer, he felt the iron grip grow tighter and he hissed in pain.

"What. Are. You. Going. To. Say."

When he finally answered, his voice was hoarse.

"I did it."

The orphanage had gained a number of sponsors over the years, and Atsushi was thrilled when they announced that they would all have a trip to the zoo. He hung around at the back as everyone got into pairs, and he kept his head low. He could feel the Headmaster's piercing gaze but it didn't dampen his mood. It was the first time in years he had ever been out of the orphanage.

As they walked around the enclosures, he couldn't help but wonder how the animals felt, trapped in a cage until their masters let them go. If they ever did. Some of the animals watched the young visitors closely, but most went about their enclosures paying little heed.

"Hey, I heard they have white tigers!" he heard one of the girls whisper to her friend. His eyes widened. White tigers? He had never heard of such an incredible thing...

"Come on, let's check it out!"

Their guides were further ahead and failed to notice the girls sneaking away. Atsushi looked behind him. The Headmaster was facing the other way, engaged in conversation with another caretaker. Emboldened, Atsushi followed the girls to see the white tigers.

He saw a crowd of people and he pushed through them, peering over the railing. The sight left him breathless. The majestic beasts were snow-white, their fur striped black and their blue-grey eyes were captivating. Something twinged in him, and it almost felt like they were looking straight at him.

He leaned over a little, his heart thudding.

What happened next - he would never fully understand, no matter how much he pondered and pored over his memories. As the crowd pushed past, he felt a push on his back.

"Good riddance." As soft as the breeze but he knew for sure he had heard it.

He fell into the enclosure and bounced onto the safety net before tumbling onto the ground, his heart quaking and his head pounding. Across the small pool, the tigers watched him. He pressed up against the wall of the enclosure, tears welling up in his eyes. He didn't want to die, not like this, no, no, no more pain.

He heard the shouts and screams above him ("Help! He fell in! A boy fell into the white tiger enclosure!") and in a split second, the pair of tigers were bounding across, towards him. He screamed when one of them grabbed his leg, and it was futile even when he tried to kick. Atsushi yelped when the other grabbed him by the collar of his shirt and he lost his breath when they dragged him across the enclosure, into the dark cave on the other side. He trembled when they pushed him in, his hands shaking so hard and his mind screaming at him to just get up and run.

There was a low growl and Atsushi cowered, his hands splayed out in an attempt to keep them away. "Please, please don't," he whispered, his voice shaking. "I won't do anything bad again so please, please." His voice cracked and his whimpers turned into sobs as he waited for his imminent death.

When he heard nothing but subsiding growls, he cracked an eye open and stared at the tigers resting on their paws, watching him. He found the strength then to scramble backwards, tears streaking his dirt-smudged cheeks. They made no movement, but one of them bared its canines. Atsushi stopped squirming and the tigers finally stood, approaching him. He flinched when warm breath ghosted over his ear. A startled squeak escaped him when he felt something wet on his neck. The tiger - it was licking his neck. The other settled next to Atsushi and let out a few rumbles (and Atsushi couldn't understand why on earth it seemed so content). When the tiger was done licking his neck, it settled heavily against him and Atsushi traced the wetness on his neck, right where the mottled bruises from a tightened chain had formed.

Why wasn't he dead yet?

When it became apparent that the tigers weren't going to do anything to him, he found himself relaxing against their warm bodies, bewildered all the while. A few minutes later, there was a crack and a few shouts and the tigers immediately shot up. Atsushi pulled himself off the ground, heart in his mouth. The beasts gently nudged him out of the cave and Atsushi tripped out, taking one last glance at the tigers, their eyes glinting in the dark.

"Young man!"

He looked out to see some of the zookeepers standing where he had fallen, their hands on something in their pockets and Atsushi half-ran, half-stumbled towards them, sinking to his knees as they tried to support him. They pulled him up quickly and Atsushi clung to them, the strength sapped out of him entirely.

"Atsushi! I was so worried!" He barely had time to register the exact moment when the Headmaster engulfed him in a tight embrace, and he felt his neck burn from phantom traces of pain. The cloying smell of antiseptic and something foul stuck to him long after the Headmaster had pulled away, his dark eyes promising pain beyond measure.

The thirteen-year-old knew for sure that his fall hadn't been a mere accident (the papers next day read: 'Boy falls into white tiger enclosure and miraculously survives!'). For a day or two, the reporters were constantly at their gates, trying to get in contact with Atsushi. Apart from the tiger incident, how was life at the orphanage? Were they happy there? The one time he had been allowed to speak to them, he plastered a smile on his face, his heart falling as the words rolled off his tongue.

"Oh yes. We're very happy here. The Headmaster... is the best."