EDITED 12-12-2014

Hello, This is FullmetalReborn. Frater Caelum in under the process of being rewritten. Chapter one has already been rewritten and cleaned up.

Future updates will be made to this story as time goes on. Thank you for reading this before you begin one of the stories I am most proud of.

If you are rereading this story, there will be changes in the chapters that follow this one as I adjust the plot and such and try to fix plot holes. I recommend reading every single chapter again as I edit. I hope you will enjoy the changes I am bringing to this story as I go on.

I thank everyone who has reviewed this story. It is my most popular and I hope I will be able to meet you expectations.

Please enjoy. The first Chapter will be posted because the succession of the rest all at once. Thank you for your patience.

BETAED BY E-CHAN&ANYANDEVERYANIME

DISCLAIMER: I DO NOT OWN KATEKYO HITMAN REBORN IN ANY WAY. I AM MERELY WRITING FOR ENTERTAINMENT PURPOSES.

Tsunayoshi lay on his stomach, his large brown eyes narrowed into the scope of his sniper rifle. He closed one eye for better view, his posture remaining absolutely still as he took in a deep breath. Years of practice made him prepared for this. The recoil, the sound - and the perfect aim. The young assassin relaxed his tense posture and tightened his finger on the trigger. He wasn't able to contain the smirk that tilted on his lips when he released the bullet and waited for chaos to occur.

As he had hoped, the piece of wood Colonello was using to lean on snapped in half. The complete horror that dawned on his face brought Tsuna immense satisfaction as the blonde tumbled forward, ramming into his second intended target. Reborn lurched forward, not able to stop the cup of coffee in his hands from splattering over his nicely tailored suit. The hitman whipped his head to the side, pitch black eyes narrowed in fury as Colonello backed away, hands raised in surrender.

When Reborn's gun came out, Tsunayoshi moved. He strapped the rifle to his back again before tossing his legs over the edge of the building. The hitman continued his torture, not letting up for a moment as Colonello continued to scream and run. The youngest assassin grinned, amused the blonde hadn't noticed his involvement in the whole situation.

Reborn, however, was another story.

His tutor immediately turned his gaze to Tsuna's hiding space, causing the brunet to jump. He tried to ignore the shiver that ran up his spine at the intensity of that look. Having known the hitman for so long, the young assassin made quick work of scaling the building, using a nearby drainpipe to help him land onto the balls of his feet perfectly. He knew what that glare meant because he had been on the receiving end of it many, many times. He could almost hear the command slipping out of Reborn's lips, 'Get the fuck down here before I put bullets in you.' Tsuna jogged over to Colonello, enjoying the pissed look the blonde was trying to pull off.

"You owe me an espresso." Reborn stated in a clipped tone. He flicked the safety on his gun, gracefully placing it into its proper hoister. He grabbed the tip of his fedora, tilting it over his eyes to cover his expression when Tsuna gazed at him smugly. Unable to handle the brunet, he quickly turned on Colonello.

"I can't believe you let Tsuna bring you down. You are truly weak." The jab at the ex-COMBUSIN member made him jump. He turned a fierce glare to Reborn to protest but was met with a very familiar green mallet. The hitman growled, loosening his tie before unbuttoning his expensive coat. He started to shrug out of it before walking off, expecting the other two to automatically follow him.

"I wasn't kidding, idiot. I want that espresso."

Tsuna fought the urge to stick out his tongue childishly but became distracted at the white van waiting for them at the end of the street. His eyes landed on the female leaning against the van. Her cape was wrapped against her small frame, reflecting off the white color of their vehicle. He gave her a wide smile, pleased when her lips turned up in a smirk. That was the closest thing he'd get as a smile from the illusionist.

"About time, I'm not getting paid overtime for driving you idiots out of here." Mammon hissed, leaning off the van before crossing over to the driver's side. She spared a glance at Reborn, the smirk on her lips widening. "Nice shirt. By the way, I heard coffee was a pain in the ass to get out."

The ebony haired male ignored her, opening the passenger door with more force than necessary.

Tsuna would have pointed out that coffee wasn't actually a pain in the ass to get out, but he was enjoying the pissed off look on his tutor.

Piss off the world's greatest hitman? Check!

However, pissing off the world's greatest hitman always had consequences.

"It's mine for a week."

The fifteen year old was horrified. He didn't even get a chance to say good bye when it was shoved into Lal's hands. Heck, he didn't even know how Reborn separated it from his body!

Lal didn't look remorseful, she dug salt into the wound when she snapped the sniper rifle into smaller pieces. The young assassin bristled, his mouth opened in protest when a hand grabbed the back of his hood. The front of his cape dug into his neck, throwing his whole body backwards. He flailed his arms in exasperation, brown eyes flickering to the irritating hitman responsible for throwing him off balance. He tried to gain his balance two more times before giving in with a sullen expression.

He stared at Lal with wide puppy dog eyes. The blue haired woman flashed him a glare, a warning look as she turned away with a very dramatic hair flip.

Damn. He had forgotten Lal took her job in disciplining him seriously. Lal Mirch was the second woman he learned to never go against... he learned that the hard way.

"We are going to visit the ninth boss of Vongola." Reborn stated, breaking the silence between them. Tsuna turned his large eyes towards the male, sagging his weight to impair Reborn's walking. "I'm taking you because I need you for the next mission and- will you stop?" The hitman hissed, pausing before he yanked the brunet onto his feet properly.

Tsuna frowned as his plan failed. He opened his mouth to make a smart-ass remark, but was met with another death glare.

It was the infamous 'don't fuck with me or I'll throw you out the window' look.

"Go on." He sighed, giving in. He couldn't deny the fact he was curious. Reborn never asked anyone to accompany him to Vongola, much less Tsuna. The young assassin wasn't a welcomed guest in large mafia families like Vongola.

If he could guess why, he would assume it was the fact he was raised by the world's strongest assassins. Most of the underground world knew him by his trademark black cloak, sniper rifle and, of course, by Caelum.

Tsuna had been five years old when the Giglio Nero family adopted him. At the tender age of three his parents abandoned him. Aria had taken interest in him and showered him with the love and affection he had been denied. Tsunayoshi was one of the unlucky kids, born with a bad lung disease. His birth parents, believing he would eventually die, abandoned him and made sure they would not be able to be traced. The only information they had left behind had been burned by Aria who had been angry when she learned he had been abandoned because his parents couldn't /deal/ with him.

But that hadn't been the only problem with him. He was known as Caelum, a mute assassin.

When Aria first invited him into the family, he had refused to speak a word. Even after Reborn healed his body, Tsuna refused to open up. It had taken a few shaky months before he was comfortable enough to speak to them. Back when he had been brought in, the Arcobaleno were cursed but Tsuna never showed it bothered him. Instead, the brunet took every word and lesson from the Arcobaleno very seriously.

His full name was a mouthful, Tsunayoshi Caelum Giglio Nero and after some thought they began to introduce him into the underground world as Caelum Giglio Nero, adoptive son of Aria. Growing with the Arcobaleno wasn't easy but he grew up to become the living legacy of the powerful carriers of the Tri-ni-sett.

As a show of thanks, Tsuna tracked down the source of the Arcobaleno curse and in doing so, he broke it.

The brunet smiled softly, looking at the teenage form of his tutor. He'd do anything to keep them all safe.

The world's greatest hitman smirked, his confidence nearly suffocating Tsuna who was by his side. Arriving at Vongola, everyone seemed intent at staring at the two teenagers walking around. Naturally, Reborn soaked up the attention like a sponge. The young assassin dragged his hood further down to conceal his face. Although a small piece of him enjoyed the fact Reborn was so content at being in his true form he still released a low chuckle to tease him. The hitman suddenly stopped, causing Tsuna to do a double take. Two large doors stood in front of them, designs imprinted into the wood with such elegance he was sure it took ages to complete. Reborn raised a fist and knocked heavily.

"Come in." A weary voice sounded as his tutor took the initiative and grabbed the door knob, pushing the elegant piece of wood open. The room was just as amazing as the rest of the mansion, heck, even the floor was crafted to perfection. Tsuna followed after Reborn and rested his hidden eyes on the lone figure behind the massive desk. Brown warm eyes gazed back at him and ease filled the young assassin's body. He knew without a doubt this was the man Reborn loved to work under, Vongola Nono.

Before they could bow, Nono was waving a hand, laughing like they were old friends when in reality, only Reborn was an old friend. "My, my, what a surprise! I didn't expect this at all, Reborn!"

There wasn't any ill intent in the boss's words, no negativity. Just pure happiness and relief. His respect for Vongola Nono skyrocketed. The boss waved a hand in front of him, gesturing to the extravagant seats. "I had been wondering what happened to the world's strongest infants." There was a teasing edge to Nono's voice and it produced an amused look from Reborn. They took a seat before Nono finally turned his attention to Tsuna. "Who is this? I had no idea you were going to take a partner on this task." There was nothing but kindness in his voice. Tsuna childishly ducked his head to hide the blush that was forming on his cheeks.

"Yes, I apologize for not informing you earlier. I asked Aria for permission to bring her son along."

The older man's eyes lit up in recognition before giving such a friendly smile that Tsuna immediately felt welcomed into Vongola. "Caelum Giglio Nero, a very talented young man. Hmm... Iemitsu should be here soon to hand you the files you will be needing." He ran a hand through his greying hair before addressing the brunet. "How is your younger sister, Caelum?"

Tsuna flushed, ducking his head shyly before looking at Reborn for help. The hitman merely crossed his arms over his chest, giving a very subtle nod. With great hesitance, Tsuna gathered his wits and spoke, "S-She's doing fine, Sir."

Nono was unable to ask another question, interrupted by the sudden knock on the door. "Come in."

A man with a buzz cut walked in. His posture and aura were professional, shoulders stiff. He adorned a neatly pressed suit, looking every bit of a Mafioso. The act was quickly broken when his blue eyes landed on Reborn, mouth hanging open like an idiot. "Reborn?! What the hell happened?!"

Tsuna would have found the situation amusing if he hadn't felt his throat dry up and his heart clench at the sight of the blonde man.

"Welcome Iemitsu. This is Caelum Giglio Nero, he will be working with Reborn on this mission." Nono broke the tension, something Tsuna was grateful for as he turned away. Iemitsu crossed over, handing the manilla folder to Reborn's waiting hands. Tsuna moved closer to view the files while the Vongola boss began to speak, "As you may know, the problem of my heir has begun to be questioned. I do not want to leave Xanxus in charge of Vongola. I love the boy as if he was my own son but I cannot entrust the future of Vongola to him. Because of this I have located the next available heir to be Vongola Decimo. According to our records, Iemitsu is descendant of Vongola Primo. This means the next eligible heir is Ieyasu Iemitsu Sawada, his son."

As if on cue, Reborn pulled out the photo of the next available heir. The minute Tsuna rested his eyes on the photo his heart clenched, a hollow feeling settling into his gut. The boy had a friendly smile to match his shinning blue eyes, and the strangest blond hair that spiked in every direction. Reborn flicked through a few more photos but the boy's face stayed in the brunet's mind.

Something ringed in his head, a voice whispering to turn tail and run. He shouldn't be getting mixed up in Vongola affairs. It made his head hurt and for the first time in his life he ignored the voice.