Title: The Unexplainable

Summary: Tsuna smiled as he listened to his fellow classmates whisper about him behind his back, Cursed-Tsuna, that's what they called him. After all, all those that interacted with him had fallen to their doom and it was only worse for those that dared mess with him. So he wondered how long the baby called Reborn would last, dark!Tsuna.

Rating: M

Pairing: Eventual R27

Beta'd by WhiteAngel128

A/N: This will follow the manga to an extent but will diverge sooner or later.

Edit: 10/18/15

Chapter 1

Tsuna huffed as he peered out at the setting sun, settled on top of a tall skyscraper where he could view the whole world beyond clearly. He could see other buildings surrounding him, but he was at the very top of the tallest of the group, meters upon meters over the ground. It was to the point where he couldn't even see the people that were walking in the streets below and could barely make out the colorful cars as they drove from one side to another.

His feet was dangling over the side of the railing, swinging back and forth without a care despite being one trip away from falling to his doom. Being so far up, the wind, as it ruffled through his brown locks gently, felt wonderful and strong enough to throw his head back. The sky above was shaded in various colors of blue, red, purple, and yellow in-between, even green. It was a wonderful view with clouds that simply enhanced the inspiring scenery, one an artist or photographer would love to capture.

Lazy honey-colored orbs stared out into the distance once he'd pulled away from the sky, continuously watching as the world darkened around him, the sun still setting slowly behind the land. It was a peaceful time despite the roaring traffic below that had been faded out by the wind, to the point where the excessive noises of people couldn't be heard at his spot. Still, it didn't matter to him, it was nice up here and the silence was what he needed for his normally chaotic life. No, not chaotic, not anymore. It had dulled over time with nothing else to do and he was falling rapidly into a routine.

'How boring…' He thought to himself as he closed his eyes for a moment to take in a deep breath of the air, filling up his lungs, and then expelled it, his shoulders slumping downwards in response. Looking around, he blinked his eyes as he felt something suddenly nudged into his mind. It was like a spark, a sensation he was familiar with, like something was tugging him from the inside. Tsuna automatically knew what it could be - there was only one explanation as to what it could be.

But how could he be called? That wasn't possible, not here. No one here knew about his existence. Well, apparently not. Tsuna blinked again, concentrating on following the feeling. His mind moved through the city, flipping around people, buildings, and anything that got in his way until he came up to a single white building, a hospital. Shifting closer, he came across a room and there he found a little boy lying on a bed all alone in the darkness, curled up in the white covers while cowering fearfully. Tsuna recognized the little being in the bed and smirked as he pulled himself back, shifting his form slightly.

"This is another world after all…" He muttered to himself, peering up at the sky in amusement. "So it wouldn't be impossible for another me to exist." After all, all worlds are connected to Hell, a world he dwelled in and called his home. It was because of this connection that it made it easy to slip into another world, bypassing the dimensions. It was simple really, no one would notice. But he was no demon, just something completely different. Still, those of the same people are interconnected whether they know of it or not and so it wasn't uncommon for those to call each other out without meaning to.

It interested him, he had never felt such a desperate attempt at calling him out, and he wanted to investigate. Looks like he found something worthwhile to take away his boredom. "Let's see the Tsuna of this world."

And so, he stood up with arms spread out wide, letting the wind gush around his body, and jumped.

Tsuna was crying silently to himself, not wanting to disturb the nurses and doctors that roamed the hallways continuously outside his door, knowing they would only say bad things about him. He curled up in the bed sheets, wanting to scream and cry out for something, anything, anyone, since it was so dark in this little room. There was hardly any light coming from the moon at the windows, the blinds wide open, and because of that, it made everything seem so scary in this place. The machines weren't helping either, they were making all sort of strange lights and sounds, clicking as fluids dripped down the lines connected to him. He was all alone in the dark. Eventually, he closed his eyes to the rest of world, hoping to tune out everything, but it didn't help.

He had learned about his condition. He was sick, so very sick, and was told that he was going to die, going to disappear. With his childlike mind, he didn't know what it meant, nor did he understand what the doctors were talking about - something called cancer? He didn't know what cancer was, but it sounded terrible. Still, to die meant that he would go far away from everyone, right? Tsuna cried harder, that wasn't fair. He didn't like this. He didn't want this.

And what about Mama? Tears streamed down his face in despair at the thought of the only person who truly loved him. Mama would be left all alone, with no one around, because Papa was never home to take care of them. Tsuna wouldn't be surprised if Papa didn't even know he was sick in the first place and probably wouldn't even come see him before he died. Such a terrible father he had.

In the end, he could only do one thing. He cried and cried some more, silently calling out to those above to help him, and prayed to someone to save him and his Mama. They were supposed to help him, right? Those people up in the sky he had been told about. Or was it all a fairytale like those kids in school told him? Just a lie?

"Crying doesn't help, you know."

A voice echoed within the small room, making Tsuna go completely still, tightening his grasp on the covers. The child, just six years old, snapped his head up to glance around the room, and sat up, thinking that perhaps the boogieman had finally come for him to take him far away before his sickness did. However, he saw no one and tilted his head in confusion. Maybe he was imagining things? Hearing voices? Had this disease really taken him?

"Over here."

Tsuna turned around to see a person sitting in one of the chairs that were against the wall with his arms crossed against his chest and blinked. The person looked just like him, except older, much older - like those adults in their twenties - with exact same hair and eyes. But there was an air around the other person, something that made him feel dark, but not evil. The younger Tsuna opened his mouth to talk and hesitated for a moment, wondering what he was supposed to ask, then shook his head to speak. "W-Who are you?"

The adult-looking male remained quiet for a few moments, eyes cold and emotionless, and examined the other thoroughly before standing up, heading over to the bed with silent footsteps. His steps were graceful, not as clumsy as the younger Tsuna's, and held an air that made people want to turn and stare. It was like he demanded obedience and attention, but at the same time, didn't. "I am you, but from another world. Heard you calling out and decided to investigate."

The younger Tsuna felt his chest flutter at those words, had his prayers been answered? Sitting further up on the bed, he tried to crawl over, ignoring all the tubes that were attached to his arms and body, and accidentally moved one of the machines with him in his struggle. He wanted to get closer to see the other, but regardless of his struggle, those machines held him back and the tugs against his skin burned. Along with moving, his body just ached worse than before, forcing his already weakened muscles to work. After all, he wasn't supposed to be moving at all, at least, that was what the doctors said.

The older Tsuna simply sighed at the sight and moved close enough to settle next to the bed with the mattress creaking at the extra weight. He reached over to push back the child's bangs to get a better look of himself and couldn't help but crack a smile at the innocence that shone in those eyes, stroking a cheek gently. To think this was how he looked a long time ago, but no longer, he had lost that innocence from his world a long time ago. Still, he couldn't help but react in kindness compared to his usual cruelty. Was it because this was a younger version of himself or was it because of those eyes? Whatever it may be, it didn't matter. It meant the same thing to him.

"Are you sick?" The older Tsuna asked, his voice calm and emotionless as he peered over the attachments carefully, looking up to read the medications' names. He didn't know what they meant or what they were used for, he was not familiar with human things. After all, in Hell there was no need for such things, though they did use something different like herbs and magic for those badly injured. Regardless, the diseases that affiliated with human race were different or nonexistent on his part due to his body structure. This latter applied to most demons as well.

"Y-Yeah, the mean old doctors say that I'm going to die. What does dying mean?" Those large eyes were peering up at his older self curiously, tears still welling up, threatening to fall down those chubby cheeks. He cuddled into that cold hand, knowing it felt great against his warm skin, and closed his eyes for a moment before reopening them to look back up.

Older Tsuna wiggled his nose at such a question, such a difficult thing to answer. "It means that you simply die. I doubt you'll understand what it means at your current age, but you'll never see anyone here ever again. "

"But what about Mama?! She'll be all alone! She'll be so sad if I were to die."

Older Tsuna tilted his head at that, what was he supposed to say to something like that? It was not something he could answer without easily saying something wrong. And so he remained quiet. He remembered his own mother, a Nana from his own world, but she had passed away a long time ago due to a tragedy. There were also others he had met and seen over the years of his existence. His eyes peered once more over little Tsuna's body, examining it carefully, and searched for something that would give him an indication of what was happening to the little one.

Cancer, he presumed, and it had clearly worked itself all over the little human body to its latest stages. It would not be long before the body gave in to the disease itself. Still, that didn't matter to someone of his caliber, he was more than powerful enough to get rid of the sickness and bring the body back to full function. But the soul… The adult male mentally shook his head, it was too late, he would not be able to save it. It was already slowly detaching itself from the physical body and if he were to tie it down, it would just get rejected, leaving the body to rot in the process.

"I can save your body, but your soul would still die I'm afraid." Older Tsuna muttered, keeping his hand on the round cheek, knowing his touch was comforting to the child before him, and crept closer.

"Soul?" Little Tsuna narrowed his eyebrows in confusion. He didn't get it, not at all. But that didn't matter, he didn't need to know. As he thought it over, he looked over his older self and got an idea. It was stupid, but if it worked then perhaps he could die peacefully. "T-Then would you be able to keep Mama company?"

This made the older one blink in surprise, pulling his hand away to stare. He clearly hadn't been expecting such a thing. "What?"

"You can stay with Mama and do what I can't, right?" There was that desperately hopeful look in those eyes, eyes that the older one realized had been his own long ago when he had been talking to a certain person. Just talking to himself was bringing back memories that he didn't want to revisit, but it didn't matter anymore, he told himself. Everyone he once knew had already passed away. Well, anyone that was mortal.

Still, he had plenty of time to waste, it wasn't like he could die and this would kill off some boredom he had been previous suffering from. After all, nothing killed an immortal faster than boredom itself. "I can do it. I have plenty of time to spare. I will heal your body and take control of it. When I find your Mama being able to live on without me, I shall leave. Would that be alright with you? These terms?"

The younger Tsuna smiled so brightly, pleased about the outcome, and was clapping his hands in joy. He wanted nothing more than to hug his older self, to whisper the words of 'thank you' over and over again. If only these machines weren't holding him back and this stupid disease wasn't making everything so painful, then he could have. So instead the other Tsuna moved, shifting closer so he could pull the younger one against his chest, and felt those tears falling down, wetting his clothes. And he heard it, the happy response. "Yes."

"Well then, if you'll excuse me, I should start the process immediately." Leaning in further, the older Tsuna placed his hands on the back of the child, rubbing it gently, before letting his fingers glow. He whispered words of a spell that he hoped would bring his younger self to a good place after he died. After all, with such a caring heart and an unselfish request, he deserved such a place. No, older Tsuna shook his head at that, the child will go somewhere nice and if he didn't, there were a few strings he could pull to ensure it. And if that didn't work, well, the threats will finish the job. He smiled lightly to himself as the body continued to cling to him, perhaps this will be a new life for him.