A/N: So I know the big crossover with this one is to cross Ryoma with Ciel, but, well, I wanted to switch things up. In my opinion, it's not too far a leap considering Ryoma's a little devil, anyway, and seems happy to corrupt others. Had to keep this superficial, though, otherwise we'd start getting into the Two-Ciels theory. Hopefully it turned out okay all the same.

Disclaimer: I own neither Prince of Tennis nor Kuroshitsuji.

Summary: Kunimitsu did not care who helped him escape the fear and agony his captors had thrown him in to. So long as they suffered and died, he would even forge a contract with the very demon the adults had been attempting to summon through his sacrifice. Kuroshitsuji AU.

Contract

Kill. Kill. Kill. Kill. Kill.

It had been his tenth birthday. It was night, he was supposed to be in bed, but, instead, Kunimitsu was running down the hallway in terror.

Ryoma! he screamed in his mind, his terror too much for words. Mother! Father!

Every time he closed his eyes to try to clear his eyes of tears, all the child was able to see was blood pooling around black fur or dying his mother's gown and hair a heavy crimson. His father's eyes stared up at him, wide and sufferingly blank.

Kunimitsu screamed.

"Someone help me! Everyone is going to die!"

Rounding a corner, the little boy saw hope in the old butler's form, but even that was momentary and dyed in red and screams of pain and terror. Everything was lost, everything came to an end, when arms wrapped around him and threw a bag over his head.

As he was carried off, Kunimitsu could hear crackling and feel an unnatural heat coming from behind him, but then it fell away like the dropping of a curtain and the next thing Kunimitsu remembered was waking up in a cell.

He was given food and water, but only enough to keep him alive. There was a chamberpot so he at least would not soil himself and Kunimitsu decided it was better to have something to separate him from a caged animal rather than break it or lose it and be forced to soil himself. There were other children, but he never saw them with the curtains kept over his cage. He only heard them cry.

The curtain lifted for food and it lifted to change out the chamberpot every day - innumerable days - until it lifted again to a masked face, words of approval and the clink of coin.

. .Kill.

There were other children, of an age, in the cell with him this time, and there was no curtain blocking light and his surroundings.

Kunimitsu almost wished that was not the case.

Watching one child after another be pulled out of the cage, tied on to a dais and then slaughtered for the enjoyment of masked and cloaked individuals made him sick, made him fear his own end, made him hate the ones who had kidnapped and sold him and the ones who had branded him. "A noble beast," they had jeered as hot iron seared his flesh. Kunimitsu had screamed in agony and they had called him cute.

Someone, he begged as hands reached into the cell and the children huddled together in the opposite corner. Kunimitsu sat separate from the rest, his back aching from the brand, his belly aching in hunger, his ankle aching from the cuff rubbing skin raw. His eyes were dead up until the point the hand grasped his arm and tugged, but however much he fought the child was too tired, too hungry, too small, too weak.

Someone, he begged as more hands held him down, lashing him to the stone altar. Kunimitsu had seen and smelt and heard enough fear and agony and death. He'd been living in nothing but that for days, months, years. He did not know how long, had no way of measuring how long, but what did chronos matter in this moment anyway?

Chanting started from the amphitheatre and the old man above him raised his knife above his head. Anyone, I don't care..just..save us… But no one came.

There was no such thing as God.

KillKillKillKillKill.

"Oh, what a little master you are. This will get interesting."

Silence fell at the voice until there was far too much noise.

"Grant me eternal life and wealth!" a fat man yelled.

"Beauty!"

"Youth!"

"Fame!"

The dark and ominous presence ignored them all, stepping up to Kunimitsu, heels clacking on blood-spattered stone in a comfortable cadence.

"You have given a big sacrifice to summon me," the cocky voice spoke, ignoring the shouts from the adults to silence the child before him as they began to realize what had happened, "This fact will not change for eternity and what has been sacrificed will never be returned. Now it's your choice "

Shock and fear turned to understanding and determination and the child cried out. "I want power! The power to take revenge on the ones who did this to us."

The shouts of the adults continued around them, but they went ignored.

"Demon, I'll make a contract with you."

The dark presence laughed, flames of darkness rising and flickering in tempo with each chuckle. "So you're abandoning the light for the path to hell?" he smirked, "Fine. Where would you like the mark? The more visible it is the more power-"

But Kunimitsu, with his decision made, did not need to hear the rest. "Anywhere is fine," he declared with a fire burning in his eyes, "I want a power stronger than anyone else's!"

Long black nails reached over and wrapped around his face. "Hmmmmm? You're quite greedy despite your age," the demon chuckled, "I'll put that seal on that eye of yours, then. The one filled with despair."

There was pain then, a pain immeasurable even compared to what he had already suffered through and Kunimitsu screamed, but afterwards, though his eye burned and bled, there was a vigor and energy flowing through his body that had not been there before.

Power.

Strength.

"This is an order," Kunimitsu commanded with all the knowledge that he would be obeyed, "Kill them!" The seal on his eye flared to life.

KILL!

It was a macabre dance, splattering crimson, and the demon proved himself adept at his orders, crushing heads and repelling attacks, his claws slashing through flesh like a chef's knife through warmed butter until there was no one left.

Even the children did not survive. If one could consider the state of existence they currently resided in as living in the first place. Kunimitsu stood and watched and his fear faded into the knowledge of what would have to be done and the confidence that he could now do it.

"What is your name?" the demon asked as they watched the building he had been kept captive in burn to the ground.

"Kunimitsu," the boy answered, "Kunimitsu Tezuka. The one who will inherit the house of the Earl Tezuka."

The demon laughed. "So that's the game we're playing? I guess I should take on a suitable form, then." The clack of heels disappeared as the demon stepped out of his masking shadow, revealing an outfit fit for a high class servant housing pale skin, dark green hair and glowing red eyes that faded like dried blood. With the flames, however, they practically glowed golden. He was the same height as Kunimitsu. Looked the same age as Kunimitsu. A servant and playmate, likely one set in training to be the future Lord's valet. "Well, then, young Lord," he smirked, "Give me an order."

"Tell me your name, then, demon."

The demon-child cocked his head and grinned his entertainment at the situation. "My name's whatever you want it to be." If Kunimitsu was not a gentleman's son, he would bet the creature was waiting for something to laugh at.

"Ryoma, then," he answered, "The name of my family's dog."

It felt good to watch the grin fall a bit on the demon's face, even if it returned all the stronger. "Hmmm," Ryoma chuckled before turning away and Kunimitsu felt a shiver as he questioned if he'd pressed this demon too far. "I prefer cats, personally." Kunimitsu's eyes narrowed as he followed the demon's lead and Ryoma chuckled once more.

I will protect you and never betray you.

I will unconditionally obey each and every order you give.

I will never lie.

But when you have had your revenge, human child, your soul is mine. Until then, allow me to die it black with the deepest of agonies and sins.