A/N: And here would the new fanfic I'm doing. -w- To those who haven't read 'The Flame That Crosses Dimensions', note that this will be very slightly connected to it, but hardly at all. You really don't need to read the other story to understand this at all. I don't even actually need to tell you this actually. Meh. Anyways, this is my first time writing most of these characters, so please, tell me if I'm messing up their personalities!

Warnings: Light swearing, occasional failed attempts at humour, and possible OOC. Hopefully I can avoid the last two though. OTL

Disclaimer: No, I do not own Katekyo Hitman Reborn. That belongs to Amano Akira. Seriously, if I did own it then I would have forced them to continue the anime. And translate the games. And have already have Tsuna sent to the past.

The only information you need to know before reading this is that Tsuna faced off against the boss of an enemy family (the Serato) in a different dimension, and has already defeated him, encasing him in ice. Besides that, no prior knowledge is needed. ^^

"Too slow, Dame-Tsuna."

Tsuna halted as once again he felt the cold press metal against his head, and the tell-tale sound of a gun being cocked. He stayed that way for a few moments, not even breathing, before the pressure lessened and he heard the guns safety click back into place. Reborn jumped off of Tsuna's shoulder and back onto the ground, as the brunette let out a defeated sigh, relaxing after the tense battle stance.

"Hmph, you've improved certainly improved a lot at fighting without your dying will, Dame-Tsuna. But still, you could still use some improvement," Reborn commented as Leon shifted back into his usual form, before placing the chameleon back onto his usual place atop the fedora. Behind him Tsuna's breathing was returning to normal since he could now take a break, rather worn out from the training, which had started at least three hours ago.

Tsunayoshi Sawada is the tenth boss of the Vongola, though he has yet to officially take over from the Ninth as he's only 16, two years having passed since he met Reborn. After he had hit 15, the Arcobaleno had started to train him to fight with his standard strength, or in other words, without having to go into normal or hyper dying will mode. A year later now, he was a competent fighter, and his performance in sports had even gone up a bit.

The two years had done little to his appearance though. His eyes were still the large brown ones, though had narrowed ever so slightly after everything that had happened since he met Reborn. His hair was slightly longer, but ever the untameable spiky mass. Unfortunately, he had only grown a few inches, and remained very much the shortest boy in his grade, even slightly short compared to some of the girls. The training he had gone through hadn't done much to rid him of his lithe form either, though by no means was he weak despite his looks. He had matured over the years as well, no longer panicking over everything, though not by much. He was still very much 'Dame-Tsuna', and it would be a while yet before he rid that title, something that Reborn liked to remind of almost constantly.

Sighing again, Tsuna opened his mouth to reply to the half compliment, half insult, but halted as he felt a twinge in his head, the feeling he always got when his hyper intuition picked up on something. Straightening slightly, brown eyes scanned the area though nothing seemed out of the ordinary. He tensed slightly in preparation, and beside him, Reborn noticed the changes in his student, and knew not to take Tsuna's hyper intuition lightly, recognizing the signs that that was what had him alert.

"Dame-Tsuna, what is it?" he asked as Leon transformed into a gun again while the infant jumped back onto Tsuna's shoulder to give him a higher vantage point.

"I'm not sure, Reborn. Something's going to show up very soon, but I can't tell what," Tsuna replied, slight nervousness showing through, but he tried to hide it with a calm face like Reborn taught him. It was silent for a few seconds, but suddenly a dark portal opened in front of the duo, causing Tsuna to jump and Reborn to blink in surprise as they recognized the darkness.

Just like they thought, four black-cloaked figures appeared moments later, all donning black cloaks, hats, and bandaged faces as well as hands. The only one who stood out would be the person in front, as the bandages were disarrayed enough to show an eye, and messy black hair came out from underneath the hat. On his shoulder sat a smaller member, the only major difference aside from size being the clear pacifier hanging around his neck. Behind them the portal closed, and Tsuna as well as Reborn were slightly relieved to see that law enforcers held no chains, hopefully meaning that they weren't here for a fight or punishment.

"Vindice," Reborn greeted, pushing his fedora up a bit in acknowledgment, though his coal black eyes still remained wary as he looked at them, the last time seeing them being during the Shimon battles. Reborn could feel Tsuna rather tense beside him, but the brunette made no move to do anything, regarding the others.

"Greetings, Sawada Tsunayoshi-kun and Reborn-kun," Bermuda greeted back with a small nod.

"It's good to see you again, Decimo, Reborn," Jager added in, while the two Vindice behind them remained silent per usual.

"Likewise. What brings you here?"

Reborn quickly got straight to the purpose, not wanting to delay finding out knowledge. Though the Vindice seemed rather friendly, they weren't people who just came to say hello, and he knew something was up. Bermuda laughed lightly, but answered just as promptly, easily able to see the unease from the two, even as Tsuna remained silent.

"Straight to the point like usual, Reborn-kun. Unfortunately, this is indeed not just a visit. Rather, we need your help for something that we can't interfere with."

The words seemed to bring Tsuna's voice back, as he also spoke up.

"You can't interfere with? How can there be something the Vindice can't intervene in?" he asked, wide-eyed, and beside him Reborn frowned slightly.

"I agree. The Vindice are the law over anything concerning mafia. No one is allowed to stop you from doing your tasks."

"That is usually the case, Decimo, Reborn. But not this time, otherwise we wouldn't be seeking your help. You remember the Serato family I'm sure," Jager began, and Reborn and Tsuna were surprised to hear the name. Ever since Tsuna had defeated their boss, Enrico Shalet, two years ago, they hadn't heard anything about the family, and had thought it disbanded at least a year ago. Bermuda nodded in agreement, and continued.

"It would seem that news of Enrico's defeat had reached them somehow roughly a year back, probably from a member that managed to get back to this dimension. We assume that it was made clear to them then that they couldn't defeat the tenth Vongola boss, what with the defeat of Enrico and all, so they had to go with an alternative to take down the Vongola. Instead of attacking the present, it appears that they are targeting the past."

Tsuna's eyes widened at that, and even Reborn couldn't help but feel a bit shocked at the news, though he quickly put his calm mask back in the place again.

"How far back?"

There was a moments silence, before Bermuda answered the question.

"Roughly four hundred years ago, the time of Vongola Primo."

The one sentence was met with silence from the other party, who were quite shocked. When it finally computed, Tsuna opened his mouth about to give his usual scream, but was stopped as Reborn shot him a glare that could rival Hibari's, the brunet managing to calm down somehow, or at least enough to work out his thoughts.

"B-but, this Vongola Primo we're talking about. He should be able to f-fight against them, and Enrico wasn't overly strong either, so I doubt his subordinates could be that strong," Tsuna managed out, and Bermuda looked at him for a moment, before answering.

"Ahh, normally that would be the case, but Giotto can't match up against weapons from our. Don't underestimate his subordinates either, they're quite strong, plus the one who was sent back was none other than Enrico's right-hand man. It also seems that the Serato have already gone into the future and taken box technology back with them, something which I'm sure you both know can only be defeated with other box weapons in most cases, basically impossible to try and get rid of with only your own strength, especially if you haven't seen them before."

Tsuna nodded in agreement to that, remembering what had happened when he and Gokudera had first met Lal Milch, easily being taken down by the pyramid prison and centipede box weapons she controlled. Reborn adjusted his fedora a bit, a look of thought on his face.

"Hmm, I understand what you're saying, but why can't you interfere?"

"While Vindice are free to imprison anyone, even going across dimensions, we aren't supposed to interfere with the past, even if the people we need to arrest are from our time. Once in a different time period, we can't do anything to them, and the past Vindice can't interfere with the Serato either, as they are from the future. While time travel doesn't go against any laws set down, it's unknown what can happen when they disturb the past, and it can have major effects on the present, easily breaking mafia laws as well. Thus, we need an outside force to help, and as it's the Vongola they're targeting, the best choice is the Vongola Decimo," Jager finished.

"W-wait, you mean, you want to send my famiglia back into the past to stop the Serato family?" Tsuna stuttered out in shock, the task seeming rather daunting to the 16 year old.

"No, only you, Sawada Tsunayoshi. Sending back too many people could make the situation worse, especially with your guardians' brash actions," Bermuda replied.

"I can't accept this then. Who knows what would happen to my dame-student if he was left alone in the past," Reborn cut in, frowning slightly, and Tsuna couldn't help but look at him in hope.

"Reborn…"

"I request to come with him."

"…" And the hope of getting out of the situation was instantly crushed, as the brunette felt a sudden urge to crouch in a dark corner. Bermuda and Jager seemed to consider the request for a few moments, before speaking up.

"Very well. So long as no one else comes, we can allow you to go back. Know that you can't give out too much information though, unless you want to risk a time paradox."

"Eh? T-time paradox?"

"Baka-Tsuna. If you give out too much information to them, even something like who you are, if you're from the future, things like that, it can change the future, or in other words our time. Your entire existence could be erased, as well as others. Time traveling to the past is very dangerous because of this, and we'll have to be careful unless we want to ruin a lot of things. Some people would also refer to this as 'The Butterfly Effect', with the idea that even if one butterfly is killed in the past, then it can change everything that should have happened."

Tsuna couldn't help but feel a deep sense of dread hearing that, now knowing the full implications of the risks. However, if nothing was done, then the Vongola would be destroyed, and probably his family line as well if they killed Primo either way, so there wasn't too much of a choice. Letting out another sigh, he reluctantly nodded.

"Thank you, Reborn-kun, Tsunayoshi-kun. We have means already to make a portal between the two time periods, and we advise you leave now, before the Serato can do anything, though not much is known about what their plans are right now."

One of the Vindice handed Jager a brown cloth bag as Bermuda talked, and he tossed it to Tsuna, who barely managed to catch it, surprised at the weight.

"The bag there contains everything that you will need in that time period, at least for a while. Accommodations will have to be figured out on your own, as well as money once you use up what we've provided you with."

"B-but, don't I need to inform the ninth and my guardians about what's happening? And I can't just disappear on Okaa-san…"

"The ninth and your guardians will be informed by us, Decimo. Also, the time passage will be different between the eras. While a week will have passed back in the past, it will only be a day here. As it is, though we found out about the Serato Famiglia's plans yesterday, they have already had a week back in Primo's time, which is why we can't delay anymore," Jager cut in, immediately quieting Tsuna's questions, the brunette only nodding again.

Bermuda raised a hand, and after a second, what almost looked like a rip in the air appeared beside Reborn and Tsuna, the inside an almost murky looking dark purple and black colour. Tsuna could feel a tug coming from it, like gravity was trying to draw him in, but he paused as Bermuda called out.

"Again, I must thank you and Reborn-kun for helping. And also, good luck. We'll come to you if you need desperate help, though it will only be when we deem it necessary."

"Hopefully we won't need it, Bermuda. We'll be going now," Reborn responded, and before Tsuna could add anything in, the infant sent a harsh kick to his head, sending him toppling into the portal as he jumped through himself. Just as the hitman got through, the portal closed with a snap, leaving behind nothing more than a few flames which quickly dispersed.

"Well, do you think they'll be okay, Bermuda?"

"We'll have to see, Jager-kun. Though I do trust that with the two of them, it should be okay. After all, they aren't Vongola Decimo and the world's best hitman for nothing."

A portal opened around them again, quickly transporting the two nameless Vindice, as Jager and Bermuda also made their way into it.

"Come though, we must inform the rest of the Vongola, as promised," the Arcobaleno finished, and the murky portal also consumed them, evaporating into the trademark flames until the entire area was left empty.

A/N: Well, was that good? I hope it wasn't too rushed; it certainly was before I revised it, and even now I'm not sure. OTL Yes, so Reborn and Tsuna will be the ones travelling back in time. :3 And a good movie (originally a short story that wasn't as complete) to watch if you want to know more about the butterfly effect is 'A Sound of Thunder'. It's more of a thriller, but really great, and this is coming from a complete scaredy cat who hasn't even had the courage to ride a roller coaster yet. OTL (Yes, I am that pathetic.) Anyways, please review and tell me what you did and didn't like about it. I always want to know about people's opinions! I just hope Bermuda and Jager were in character… The next chapter should be up soon, but until then, ciao!