This idea has been in my head for ice ages and I just now got inspired to write it. Human!AU where Leonardo has been raised by Splinter, Raphael and Karai by Shredder, Donatello by Baxter Stockman, and Michelangelo by the Kraang. Leonardo has been told all his life that he had to find his brothers and save them, but they don't want to be saved.

I do not own TMNT, otherwise Casey Jones would have never happened. Also, comments make my day and criticism is welcome.

"Karai, Raphael!" Shredder's sharp voice rang through the room, stopping both of them in their tracks as they strolled into his throne room. Still casting glares at each other out of the corner of their eyes, they knelt in before him and ducked their heads submissively.

"It was his fault, Father!" Karai protested immediately, pointing an accusing finger at the boy next to her. "If it weren't for his temper, we wouldn't have been seen by those Purple Dragons!"

"My fault?!" Raphael started to rise, hands clenched in fists as his electric green eyes burned. "That's the thanks I get for defending your honor? Those creeps were – were – verbally undressing you!"

"I can defend my own honor, thanks. And all they were doing was saying I'm hot." Karai flicked her bangs away from her face. "Which is more than you can say, anyway." Reaching over to him, she yanked up his left sleeve, the only sleeve he had. It revealed a scaly green arm. "You wouldn't be too bad except for this deformed arm of yours."

A low growl escaped Raphael's throat. "Just because it looks weird doesn't mean I can't ram it SO FAR-"

Shredder stamped his foot. The floor shook, stopping both of them in their tracks. "Silence, both of you! I have no time for your quarrels or your failures. Get out there again now!"

"Yes, Father," the two of them chorused, bowing low in front of him before scuttling along side-by-side as if they had never argued.

Their petty fights were common, but Karai sensed she had deeply injured her bad-tempered brother. He had pulled his sole sleeve over his scaly arm and refused to look at her as they exited Shredder's tower.

Hating herself for what she was about to say, Karai cleared her throat. "Look, I appreciate what you were trying to do, but we can't risk our mission for a tangle with a bunch of stupid street punks. And you don't look that terrible, if it means anything to you."

Raphael glanced over at her sullenly. Karai had only been a year old when he was born, but she remembered doubting they were actually siblings once they got older. While she had black hair, Raphael's was fiery red, and his green eyes looked nothing like her dark ones. Regardless of whether or not they were actually related, he was her little brother through and through.

"Hmph. You really think I'm so shallow that I would care what I look like?" he grumbled, folding his arms.

"You do wear that stupid sleeve. If you don't want to look so suspicious, wear one on your other arm – or are you trying to show off your muscles?" she badgered him, earning herself a rough punch in the arm.

"Let's just get on with the mission, alright?" he groaned, rolling his eyes. "We gotta find Hamato Yoshi and bring him back to Father."

Karai relented and nodded. "Right. Let's start where we left off. And roll your sleeve up – you might as well show off your arm. It's got to be the only one in the world anyway."

In an old warehouse not too far away from where the Oroku siblings were slipping through the shadows, Michelangelo skateboarded recklessly through the concrete hallways. To help with balance, his arms were stretched to both sides of him –a pale, freckled arm and a green, scaled one. He whooped as he whizzed past the robots parading through the halls.

"Look out, Kraang! You too, Kraang! And you! Sorry!" he called over his shoulder as a pink, squirming alien hissed at him as he passed.

"Michelangelo!" a female human voice bellowed through the halls. Momentarily paralyzed with fear, the boy failed to turn the next corner and rolled headfirst into the wall.

A young girl with black and purple hair strolled up to the tangled mess that was Michelangelo and peered at him over the frames of her rhinestone-studded glasses. "Seriously? This is the most you can amount to? You're not only skateboarding indoors, but you can't even do it without running into a wall?"

Rubbing the back of his head, Michelangelo struggled to his feet. "Sorry, Mom – I mean, Kraang Subprime," he corrected himself, only somewhat repentantly. She folded her arms and glared up at him.

"Three things. One, I'm not your mother. Two, I'm actually male; I just have to take this stupid female form for work purposes. Three, I have to go third wheel on April and Casey's date, which means you're in charge of the base until I get back. Screw up and I take another scale off your arm."

Michelangelo flinched and rubbed his deformed arm. Several scales were already missing from it due to previous times he disobeyed, messed up, or been too annoying. They would grow back eventually, but the extraction process was quite painful. "Okay, okay." He scowled for a moment before his infectious smile returned. "Hey, can't you leave Kraang in charge this time and let me come along on your date third-wheeling? It would be good practice for me! I could work on my stealth training by staying in the shadows and not getting caught!" He ruffled his wavy blond hair and struck a pose, his blue eyes twinkling. "Just call me Doctor Stealth-instein!"

Kraang Subprime slapped her forehead. "Ugh. Fine, whatever." She collared a nearby robot. "Kraang, you're in charge. Michelangelo, with me – but get your jacket first to cover up that hideous arm of yours."

"No problem-o!" Michelangelo tugged off a neon orange jacket that was tied around his waist and slipped it on. "Done!"

Taking a deep breath, Kraang Subprime adopted a teacher's patronizing voice. "Think, Michelangelo – just don't injure yourself in the process. If you're going on a stealth mission, what's wrong with that jacket?"

A puzzled expression crossed his freckled face. "Uhhh… um… hrm… Oh! I know! The sleeves are too long!" He waved his arms, letting the extra fabric covering his hands flap around.

"No, it's too bright! It's brighter than you are – although practically everything is. There's no way to hide in the shadows if you're wearing a jacket the color of a tangerine! Just – just get a black jacket and follow me, I'll be at the front door." Kraang Subprime let out a sigh of defeat. Michelangelo flashed her a thumbs-up and a smile.

"Got it!"

"Donatello, are those chemicals ready yet?" Baxter Stockman drummed his fingers anxiously on the lab table.

"Just about, Dad. One second… here we are!" His son presented him with a vial filled with an orange liquid, a gap-toothed smile on his face. The two of them crowded around a beaker bubbling over with some clear fluid.

"If this doesn't explode when we mix them, it'll be safe and will definitely work this time!" Baxter declared, sniggering. "We are geniuses, Donatello! Safety glasses?"

"Check!" The black-haired boy pulled the goggles off of his head and over his eyes. Baxter did the same, gloved hands trembling as he tipped the vial.

Donatello lowered his voice to an excited whisper. "If this works, will I finally be able to go outside without wearing long sleeves? It's way too hot for that."

"Yes, and you fulfill your part of the deal by cutting off that stupid braided long hair of yours," Baxter grumbled. Hesitantly, he poured the orange liquid into the bubbling clear fluid.

For a moment, they could have heard a pin drop. The bubbling ceased as everything turned a vibrant shade of magenta. Both Baxter and Donatello took a frightened step backwards.

"Is it safe?" Donatello asked in a hushed whisper, clinging to his father's arm like it was a lifeline. Baxter shook him off.

"I think s-"

His sentence was abruptly cut off by a massive popping sound, and smoke filled the room for just a moment. It disappeared, leaving both father and son in the fetal position on the floor.

"And that's why you don't think," Donatello quipped light-heartedly. Baxter pulled himself to his feet, using the lab table as a crutch, and examined the beaker. The glass wasn't damaged, but all the liquid inside it had vaporized.

"Not again!" the man whined, ripping his safety goggles off and tossing them on the floor. "Your hair lives for now, boy." He stalked off, leaving his son to clean up the mess they had made.

"Ah, well," Donatello sighed, amber eyes surveying the lab table. He pulled up the left sleeve of his white lab coat to look at his scaly green arm. "Guess I'm stuck with you for a little while longer."

In the training room in their home in the sewers, Leonardo sat in a meditative position across from his teacher.

Clear your mind, Splinter had always insisted. Think of nothing.

Yet he couldn't. Instead, his rebel mind wandered. This is stupid. I shouldn't be sitting here. I should be training! I should be searching the streets of New York for my brothers! Sensei tells me that I have to find my brothers and save them, but he'll barely let me outside! How am I supposed to help them if all I do is sit here and think of nothing?

A sharp pain over his head jarred him into reality, and he let out a small wail of pain. "Sensei?!"

Scowling, Splinter looked down at him, cane in hand. Tall and imposing, he was as wise as he was strong. It was only his lame right foot that held him back – the disability that chained him, one that he had earned on the field of battle against his enemy Oroku Saki. "You are distracted, my son. I have told you before. You must clear your mind."

Leonardo struggled to his feet, blue eyes troubled. "Sensei, I don't mean to question your judgment, but shouldn't I be out there, looking for my brothers? I don't know how I'd find them because I've never seen them before, not even in pictures, but searching blindly has to be more useful than sitting here and thinking of nothing."

Splinter let out a deep sigh, pinching the bridge of his nose. "You will know your brothers because they will have the same arm as you. But we have had this discussion before, Leonardo. You are not yet ready to face the dangers that this quest will present. There is time to train and prepare."

"I've been training and preparing my whole life! Fifteen years, Sensei! I know I've asked this before, but please, please let me try to find them. You've told me that I have to help them ever since I was a child, so please just let me." Leonardo dropped to his knees and bowed his head pleadingly, fists clenched tightly.

Splinter turned and strode a few steps away, thinking. After a moment of consideration, he posed another question. "Why do you want to go so badly?"

Well, for one I'm sick of being stuck down here in the sewers of all places with nothing to do but train, but that's not the main reason. Leonardo took a deep breath. "I want to help them. You said you don't know what happened to my brothers and that you just knew that they were in trouble. I might not know them, but they're my brothers, and I want to help them. I want to know them. I want to know my family."

Splinter knelt down in front of his son, searching his clear sapphire blue eyes. "…Yes… Yes, my son, Leonardo. I believe you are ready. Tonight, under the cover of darkness, you may go out into the city. My own injuries prevent me from leaving these sewers, not to mention Oroku Saki's men are searching for me everywhere… You must be cautious, my son. I trust you to take care of yourself. Please do not break my trust."

"I won't, Sensei." Leonardo hid his excitement and relief under a calm mask. A ninja was always in control, especially of himself.

That night, as Leonardo climbed out of the sewers and breathed in the fresh, crisp night air, he made a vow. My brothers… Raphael, Donatello, Michelangelo… I will find you, wherever you are, and I will save you.