Disclaimer: I do not own Katekyo Hitman Reborn!

A/N: This is the most times I've ever typed 'Byakuran' and 'Tsuna' in one sitting...

The consequences of his actions during his final fight against Byakuran did not fully descend upon Tsuna until about three days after returning to a peaceful past with his comrades. It was a swift and sudden revelation that hit him like a ton of bricks without warning on a Sunday afternoon, and he had not been mentally prepared for it in the slightest. He figured his friends knew about this all along (after all, they had witnessed the fight itself), but they had probably said nothing for Tsuna's sake. Tsuna had just wanted to forget everything that had happened in that horrific battle, and think of only the good times he had spent in the future, but unfortunately, guilt was something that was very difficult to dispose of. Especially the guilt of murder.

'...I killed him...'

The handheld videogame in Tsuna's hands fell to the floor with a light thud. Lambo and Tsuna's mother both turned their heads in the young teen's direction, quizzical looks expressed on their faces. The color in Tsuna's cheeks slowly drained away, and in its place came a sickly pale hue of white. He started to break out into a feverish sweat. Tsuna felt a powerful scream rising in his throat, accompanied by acidic bile, but he held back so as not to frighten the others, so blissfully unaware they were. Tsuna envied them at that moment.

'I killed him...I...' the thought itself was so paralyzing, so inexplicable, that he had to repeat it over and over in his mind so he could fully understand it, '...I...I killed him...I killed Byakuran back then...in the future...in cold blood...I murdered him...blew him to smithereens...he's dead...'

Tsuna could not hold it back much longer. Jumping to his feet, his body shaking violently all over, Tsuna ran for the bathroom with all of his might. His mother cried out his name as he went into the hallway, but he did not reply, because if he opened his mouth now, then instead of words there would be vomit spilling out. Tsuna nearly tripped once on his way to the bathroom, but he was fortunate enough to make it there just in time. Tsuna locked the door behind him as he went in. He leaned his head into the toilet bowl as he thrust his lips apart and allowed the partially-digested puke to pass on through. The smell of it was vile, and it made Tsuna's eyes burn and his stomach ache. He started to weep.

"Oh god...oh god...I...I killed...killed him..." He tried to speak, but found it extremely difficult. Tsuna could barely catch his breath. His heart was pounding so fast and hard it felt like it was going to burst out of his chest at any moment. He heard someone knocking on the bathroom door behind him, but he did not even have the strength of will to move from his spot. Tsuna's eyes were sparkling brightly with tears as he thought of that battle; it seemed like it had been so long ago.

He had been so distraught over the sudden loss of Uni and Gamma, and the fact that they had sacrificed themselves to stop Byakuran, that Tsuna had become blinded with his own rage, his own sadness. He knew that, if anything, Byakuran deserved nothing less but death after everything he had done to the people of Japan, but Tsuna had sworn he would not allow this new generation of Vongola to go down a path of unnecessary violence and bloodshed. None of his guardians had ever killed anyone, and Tsuna did not want them to be burdened with the emotional and mental agony of having to take a person's life. It was so tragically ironic in Tsuna's view that he had to be the one who killed first, despite him being the one most against such actions.

"There could have been...a better way..."

Deep down, Tsuna knew that there had been no other way. The only possible way to have brought an end to Byakuran's reign of terror was to kill him, and Tsuna knew that, but he didn't want to accept such a fact even now. No matter how many words Tsuna could speak, no matter how many punches he could throw, no matter how angry he could become...he could not change Byakuran. Byakuran had been firmly set in his insane beliefs of power, and he was in far too deep for anyone to be able to save him. Byakuran's death was the only choice. For a short time, Tsuna had tried to convince himself that Byakuran had it coming to him, and he was a lost cause, but that still couldn't hide the fact that Tsuna was the one who utterly annihilated him.

"What about...what about the other Byakurans...?"

Tsuna recalled that if Byakuran in the future was destroyed, then so would all of the Byakurans of the parallel worlds. While he was still rather fuzzy on the details of all this alternate-universe business, Tsuna figured that this meant that he had actually killed a multitude of people all at once, and all of them were Byakuran. He wasn't just a murderer, but a mass murderer. Even worse for him to think about: was every Byakuran in the parallel worlds evil? Could there have been a good Byakuran in one of those worlds, so far away that not even the real Byakuran knew of it? A kind, caring Byakuran who only wished to help people? Was there such a possibility? He didn't have to die then, right? And wasn't Ghost a Byakuran from a parallel world? Did his death count, or was he already dead and nothing more than a walking mass of Dying Will Flames? These questions spun around and around in Tsuna's mind like a hurricane.

Tsuna knelt down on the floor in a position similar to someone begging. He buried his face into his hands, choking on his own pitiful sobs. He had worked so hard to return to the past, but at such a heavy cost. No matter how many times he might try to make himself believe that killing Byakuran was completely justified, he would not be able to believe it. To have murdered someone like that for his own purposes, and then to take joy in winning in such a way...it made him no better than Byakuran. That very thought terrified Tsuna like nothing else ever had. There was no longer anyone knocking on the door. His mother was probably calling for help, or something of the like, the boy figured.

"I'm...sorry...so sorry..."

Tsuna had once believed he could stop the legacy of bloodshed associated with the Vongola family, but...how could he even do that, if he was someone who had already stained his hands with the blood of another?

No answer came to him.